The present invention relates to a prefabricated boat. The prefabricated boat comprises a body part being composed of a plurality of division members capable of being assembled, an armor part for wrapping around and fixing the body part assembled into a single body, and an air tube mounted on a desired position of the inner face of the armor part. The armor part has the form of a bag and is provided with an opening for receiving the plurality of division members constituting the body part. Air is injected into the air tube to expand it in the state that the armor part wraps around the body part. Due to the expansion force of the air tube, the division members constituting the body part are fixed firmly, thereby preventing the relative movements between the division members.