A pair of running rails (46) each having upper and lower sides are laid from the ground (44) into the water (45). Main tires (12) which are positioned between the upper and lower sides of the running rail (46) and are brought into contact with the lower side of the running rail (46) when it runs on the ground, are rotatably disposed on sides of a main body of a running vehicle (1), and auxiliary tires (13), which are brought into contact with the upper side of the running rail (46) by virtue of the buoyancy of the running vehicle main body (1) when it runs in the water, are disposed such that they are brought into contact with the main tires (12). The running vehicle main body (1) can continuously run from the ground into the water by moving the running vehicle main body (1) along the running rails (46) by driving and rotating the main tires (12).