To provide a joint structure capable of easily and reliably connecting two parts when a longitudinal insertion member is inserted into and connected to a member to be inserted.

In this joint structure, in order to connect the insertion member 20 having a projecting part 23 longitudinally extending from the longitudinal front end outer peripheral portion and the member 30 to be inserted having an annular groove 37 which includes a contact surface 36 in contact with the projecting part 23 and a continuous surface extending radially outward from the contact surface 36 and is formed at the end of an insertion hole 35 in which the insertion member 20 is inserted, the insertion member 20 is press-fitted into the member 30 to be inserted, and the projecting part 23 in contact with the contact surface 36 is deformed and locked to the annular groove 37.