The present invention provides a mounting tube for a top guide. This mounting tube (20A1) for a top guide has: a center axis (CA) extending in the longitudinal direction a first insertion opening (120) provided on one end in the longitudinal direction a rectangular second insertion opening (130) provided at the other end in the longitudinal direction and an inclined surface (140) provided on the other end. The tip of a fishing rod is inserted into the first insertion opening (120). An insertion leg of a frame for supporting a guide ring is inserted into the second insertion opening (130). The rectangular center of the second insertion opening (130) is separated from the center axis (CA) in the upward direction. The inclined surface (140) is in contact with the second insertion opening (130) and is inclined at an acute angle to the center axis (CA).
