To provide an arterial blood collecting kit which ensures mixing of a blood with an anti-clotting agent at the time of taking blood of an artery, is free of bubble generation caused by a jetting stream of blood, and which allows the air in the blood introducing space to be exhausted completely.

The arterial blood collecting kit is composed of a blood collecting needle 1, an outer cylinder 2 having a needle mounting part 21, a plunger 3 inserted in the outer cylinder 2, a gasket 4 coupled with the tip of the plunger 3, a filter 5 which is installed at the joint between the head 31 of plunger 3 and a rod 32 and which transmits gas and does not transmit the blood, and an anti-clotting agent 6 which is in solid state and is accommodated in the hb 11 of the needle 1. The plunger 3 is equipped with an exhaust hole 33 in communication with the external air, while the gasket 4 is furnished with a communication hole 41 to put the space bounded by the front end face of gasket and the outer cylinder 2 in communication with the exhaust hole 33.