A flexible tube insertion apparatus includes: a flexible tube to be inserted into an insertion target body; a state detector to detect state information of the flexible tube relating to a shape of the flexible tube; and a bent formation determining section to determine whether first and second bent portions bent in different directions are formed on the flexible tube based on the state information. The flexible tube insertion apparatus further includes a shape changing section, arranged in the flexible tube, to actively change the shape of the flexible tube so that an angle at which a first virtual flat plane on which the first bent portion is formed and a second virtual flat plane on which the second bent portion is formed intersect becomes smaller, when the bent formation determining section determines that the first and second bent portions are formed on the flexible tube.