Disclosed is a percussion lock installed on a firearm, and more particularly, to a percussion lock wherein the hammer is operated through a link member so that operation of the firearm is possible in a small area, making it possible to design a firearm flexibly and reducing the volume and weight of the firearm. According to the present invention, the percussion lock installed on a firearm to fire a bullet by hitting a firing pin comprises a housing mounted in fixed state to a firearm, a hammer installed on the upper part of the housing for hitting a firing pin, a link member linking the hammer and the housing so that the hammer moves on a curve maintaining horizontal state, and an elastic member supporting the link member with elastic force.