Provided are a reinforcing method and a reinforcing structure for a manhole having a neck part in a position shifted from the middle part of an upper slab which allow the buried manhole to be reinforced sufficiently against stress inflicted thereon while reducing the operation and material costs involved in the reinforcement. The manhole reinforcing method according to the invention is a method for reinforcing a manhole including a rectangular trunk part having an upper slab, a sidewall, and a lower slab and a neck part provided in a position shifted from a middle part of the upper slab of the trunk part, the method includes providing a strip-shaped reinforcing member of reinforced fiber at the upper slab and the lower slab while refraining from providing the strip-shaped reinforcing member at the sidewall, and fixing an upper part of the sidewall and the upper slab and a lower part of the sidewall and the lower slab each by a reinforcing member at the middle part of the sidewall in the longitudinal direction of the trunk part.