A reciprocating saw blade mounting device includes a reciprocating rod, a clamping mechanism and an ejection mechanism. The reciprocating rod is provided with a clamping cavity. The clamping mechanism includes a clamping member and a positioning member which are disposed opposite to each other. The clamping member can move such that the reciprocating saw blade mounting device switches between a clamping state and a released state. The ejection mechanism includes a pressing block and a first elastic member. When the reciprocating saw blade mounting device is in the released state, the pressing block is elastically pressed between the clamping member and the positioning member by the first elastic member. When the reciprocating saw blade mounting device is in the clamping state, the pressing block is pressed out from between the clamping member and the positioning member by the clamping end and compresses the first elastic member.