A machining method and coupling structure for a fiber reinforced plastic structure member (1) obtained by narrowing an end of the member (1). Also included are a reinforcing member (4) which inhibits expansion by adhering to the outer circumference of the narrowed portion of the fiber reinforced plastic structure member, a locking member (2) which is provided with a through-hole (2a) in an axial direction and which fits into a narrowed portion (1a) of the fiber reinforced plastic structure member 1, a coupling anchoring member (3) which is provided with a rotation stop on the side thereof, and a spacer (5) which restricts only a rotation of the coupling anchoring member (3) and which is attached between a member (7) to be coupled and an end of the fiber reinforced plastic structure member (1) by passing the coupling anchoring member (3) through so as to slide in the axial direction.