This study targeted the effects of heat treatment on the mechanical properties of high-strength steel bolts. High-strength steel bolt samples were manufactured by sequential cutting, cold forming, heading and heat treatment. All sample bolts were M12, and the material was 30MnB4. During the heat treatment, quenching and tempering were applied to high-strength steel. Stress-strain curves were obtained for the steel bolt samples after different heat treatments. The mechanical properties of the steel bolts, such as yield strength, tensile strength, hardness and elongation, were determined for the various heat treatments. It was concluded that heat treatment is an important process that changes the microstructure of the steel bolts and their mechanical properties. By heat treatment at different temperatures it is possible to obtain high-strength steel bolts with different properties.