To provide a connection structure having simple construction permitting easy and accurate connection of a pipe to another member.

A plurality of protruded strips 4a, 4b formed along a circumferential direction with their diameters smaller than the inner diameter of a socket 7 of another member 3 are provided on the outer peripheral face at the front end of the pipe 4. The outer diameter of the protruded strip 4a located on the front end side is set smaller than the outer diameter of the protruded strip 4b located on the base end side. An O-ring 8 to be fitted to the socket 7 with a preset interference is held between the neighboring protruded strips 4a, 4b and a clip 9 to be anchored on the surface of another member 3 is provided on the outer periphery of the pipe 4. The connection of the pipe is completed only by putting the pipe 4 into the socket 7 until reaching a position restricted by the clip 9 and then anchoring the clip 9.