Penelitian ini adalah penelitian kualitatif deskriptif yang bertujuan untuk menganalisis penerapan model Problem Based Learning (PBL) guru matematika pada materi luas permukaan tabung. Subjek penelitian ini adalah satu orang yang dipilih secara purposif dari tiga orang guru matematika kelas IX SMP. Instrumen penelitian ini yakni peneliti sendiri, lembar observasi, pedoman wawancara, dan dokumentasi. Data dalam penelitian ini dianalisis dengan tiga tahap yakni kondensasi data, penyajian data, dan penarikan kesimpulan & verifikasi. Hasil penelitian menunjukkan bahwa guru sebagai subjek penelitian yang menerapkan model PBL di kelas tidak sepenuhnya sesuai dengan teori. Guru memberi perlakuan berbeda terhadap kedua kelas penelitian karena perbedaan kemampuan matematika siswa pada kedua kelas (ketidakadilan epistemik). Juga penerapan model PBL tidak berjalan sebagaimana mestinya dalam pembelajaran. Hal ini karena, di satu sisi masih kurangnya kemampuan siswa dalam memahami konteks masalah yang diberikan oleh guru. Di lain sisi, guru masih terbiasa dengan pembelajaran secara konvensional. Oleh karena itu, guru masih cenderung mendominasi kegiatan pembelajaran. Padahal, aktivitas pembelajaran mestinya didominasi oleh siswa.Kata kunci: Problem Based Learning, Guru Matematika, Penerapan Model, Luas Permukaan Tabung.This is a qualitativedescriptive research that aims to analyze the application of the Problem Based Learning (PBL) model of the mathematics teacher on the surface area of the cylinder. The subject of this study was just one person who was selected purposively from three mathematics teachers of grade IX at SMP. The research instruments were the researcher herself, observation sheet, interview guide, and documentation. The data in this study were then analyzed in three stages, namely data condensation, data presentation, as well as conclusion and verification. The results of the research show that the teacher as a research subject who applies the PBL model in class is not fully in accordance with the theory. In addition, she treats the two research classes differently because of the differences in students' mathematical abilities in the two classes (epistemic injustice). Also, the application of the PBL model does not work as it should be in learning. This is because, on the one hand, there is still a lack of students' ability to understand the context of the problem given by the teacher. On the other hand, the teacher is still accustomed to conventional learning. Therefore, the teacher still tends to dominate learning activities. In fact, learning activities should be dominated by students.Keywords: Problem Based Learning, Mathematics Teacher, Application of The Models, The Surface Area of The Cylinder.