A chemical liquid injector comprises liquid syringe 200 and a chemical liquid injector. Liquid syringe 200 has cylinder member 210, a piston member and RFID tag 230 put on an outer circumference of cylinder member 210. The chemical liquid injector has cylinder holding mechanism 120 for holding cylinder member 210, a piston driving mechanism for driving the piston member and an RFID reader. The RFID reader has reader antennas 132L, 132R placed opposite to a tag antenna so as to be able to receive data from RFID tag 230 with cylinder member 210 is appropriately held by the cylinder holding mechanism. The piston driving mechanism is permitted to operate only when the RFID reader receives data from RFID tag 230.