Qualified learning materials is needed in the efforts to improve the quality of teaching-learning mathematics. Qualified learning materials can be obtained through development research. Learning materials in this study were learning materials that were developed based on guided discovery learning model. The learning materials was also developed by integrating local culture into a guided learning model. The local culture in this study was adapted to the local culture of the students, namely the Batak Toba. Learning materials in this study were developed using the development model of Thiagarajan et al. (1974). The result of second trial showed that learning materials based guided discovery learning with Batak Toba context improved students' mathematical problem solving ability and self-efficacy significantly. Based on the results of the study, it was suggested that mathematics teachers make an effort qualified learning materials and integrate local culture in mathematics learning.