An apparatus for detecting tissue hardness of a living body includes a housing, a cap, a bottom cover, a driving module, a buffering module, a spring pipeline, a push-rod and a detecting module, and the driving module includes a firing spring and a restoring spring, and the two springs have different rigidities so as to form a reciprocating structure of the firing mechanism. After the detecting module of a firing mechanism is triggered, the resilience of the restoring spring compresses the firing spring back to its firing length, so as to restore its position by a single driving point and allow users to complete the firing operation by one hand and simplify the operation of doctors to improve convenience and efficiency.