An attachment tube for a top guide has a central axis extending in a longitudinal direction, a first insertion opening provided at one end in the longitudinal direction, a rectangular second insertion opening provided at the opposite end in the longitudinal direction, and an inclined surface provided at the opposite end. A tip portion of a fishing rod is inserted to the first insertion opening. An insertion leg of a frame supporting a guide ring is inserted to the second insertion opening. A rectangle center of the second insertion opening is spaced upward apart from the central axis. The inclined surface adjoins the second insertion opening and is inclined at an acute angle with respect to the central axis.
