A connection mechanism includes a first member, a second member and a cylindrical third member which connects the first member and the second member to each other. The third member includes a protrusion portion and a second connection portion. A held portion of the second member is inserted from the one end portion to the third member and the held portion is disposed in a space portion between the protrusion portion and an end face. In this state, the third member holds the held portion between the end face and the protrusion portion thereby the third member is moved the protrusion portion relative to the first member and the protrusion portion presses the held portion against the end face.
