A reciprocating pump, which introduces a transfer fluid to a pump chamber via a suction valve and discharges the transfer fluid from the pump chamber via a discharge valve by reciprocating movement of a reciprocating movement member facing the pump chamber, the reciprocating pump comprising: a pump head having the pump chamber; a first connection port provided on a transfer fluid suction side of the pump chamber; and a second connection port provided on a transfer fluid discharge side of the same, the first and second connection ports communicating with the pump chamber; the suction valve comprising a valve cartridge, the valve cartridge containing a ball valve having a valve seat and a valve ball, wherein the valve ball is disposed above the valve seat and closes the valve seat by its own weight, an upper portion of the suction valve being housed in the first connection port; the discharge valve comprising the valve cartridge, a lower portion of the discharge valve being housed in the second connection port; a first connecting adapter, which is disposed on a lower side of the suction valve, has a third connection port housing a lower portion of the suction valve internally and connects the suction valve with the first connection port; and a second connecting adapter, which is disposed on an upper side of the discharge valve, has a fourth connection port housing an upper portion of the discharge valve internally and connects the discharge valve with the second connection port, characterised in that at least one rib extending in a connecting direction of the valve cartridge is provided on each of inner sides of the second connection port of the pump head and the third connection port of the first connecting adapter; at a lower outer periphery of the valve cartridge, at least one slit which extends in the connecting direction and into which the rib is loosely inserted is provided, and relationship (id2b, id3b) > od1t > (id1, id4) > od2 > (id2t, id3t) > od1b is satisfied, wherein an inside diameter of the first connection port is id1, an inside diameter of the second connection port is id2b, an inscribed diameter at a top of the rib of the second connection port is id2t, an inside diameter of the third connection port is id3b, an inscribed diameter at a top of the rib of the third connection port is id3t, an inside diameter of the fourth connection port is id4, an outside diameter of the lower outer periphery of the valve cartridge is od1t, an outside diameter of a bottom of the slit at the lower outer periphery is od1b, and an outside diameter of the upper outer periphery of the valve cartridge is od2. a pump head having the pump chamber; a first connection port provided on a transfer fluid suction side of the pump chamber; and a second connection port provided on a transfer fluid discharge side of the same, the first and second connection ports communicating with the pump chamber; the suction valve comprising a valve cartridge, the valve cartridge containing a ball valve having a valve seat and a valve ball, wherein the valve ball is disposed above the valve seat and closes the valve seat by its own weight, an upper portion of the suction valve being housed in the first connection port; the discharge valve comprising the valve cartridge, a lower portion of the discharge valve being housed in the second connection port; a first connecting adapter, which is disposed on a lower side of the suction valve, has a third connection port housing a lower portion of the suction valve internally and connects the suction valve with the first connection port; and a second connecting adapter, which is disposed on an upper side of the discharge valve, has a fourth connection port housing an upper portion of the discharge valve internally and connects the discharge valve with the second connection port, characterised in that at least one rib extending in a connecting direction of the valve cartridge is provided on each of inner sides of the second connection port of the pump head and the third connection port of the first connecting adapter; at a lower outer periphery of the valve cartridge, at least one slit which extends in the connecting direction and into which the rib is loosely inserted is provided, and relationship (id2b, id3b) > od1t > (id1, id4) > od2 > (id2t, id3t) > od1b is satisfied,