To provide a connection structure of medical container collecting and storing medical fluid capable of transferring chemical by composing it of a cap sealing an inlet and a connection shaft which is connected to a part of another one to be connected.

A chemical liquid flow path 5 communicated with a lateral hole opening 6 being formed in the outer circumferential surface starting from a shaft end to the vicinity of a rear end is provided in the center of a rubber cap 1. A needle type connection shaft 2 having a flange 9 at its end is inserted in the cap 1. The flange 9 is in contact, at its out ercircumferential face, with the inner circumferential surface of a shaft holder 11 installed upright on the cap 1 fitted to the opening of a container 13.