An endless-track traveling apparatus comprising: a first pulley and a second pulley that are arranged in such a way that the respective center axes thereof are in parallel with each other; a motor that drives at least one of the first pulley and the second pulley ; and an endless track that is wound over an outer circumferential surface of the first pulley and an outer circumferential surface of the second pulley , that is driven by the at least one of the pulleys rotated by being driven by the motor , and that travels over the first pulley and the second pulley , wherein an outer circumferential surface of the endless track is configured such that it makes contact with a traveling subject so that based on the travel of the endless track , the endless-track traveling apparatus travels on the traveling subject , wherein there is provided a planar member that is disposed in a space surrounded by the endless track and has a flat portion that makes contact with an inner circumferential surface of at least one of two portions, of the endless track existing between the first pulley and the second pulley , that face each other, wherein the flat portion of the planar member makes contact with the inner circumferential surface of the endless track at a position at the traveling subject side with respect to a virtual straight line (X1) that connects a vertex (A1), at the traveling subject side, in the outer circumferential surface (33a1) of the first pulley and a vertex(B1), at the traveling subject side, in the outer circumferential surface (33b1) of the second pulley , wherein at least part of the outer circumferential surface, of the endless track , that faces the inner circumferential surface being in contact with the flat portion of the planar member is configured such that it makes contact with the traveling subject , characterized in that the endless track is formed in such a way that the hardness of the inner circumferential surface is larger than the hardness of the outer circumferential surface. a first pulley and a second pulley that are arranged in such a way that the respective center axes thereof are in parallel with each other; a motor that drives at least one of the first pulley and the second pulley ; and an endless track that is wound over an outer circumferential surface of the first pulley and an outer circumferential surface of the second pulley , that is driven by the at least one of the pulleys rotated by being driven by the motor , and that travels over the first pulley and the second pulley , wherein there is provided a planar member that is disposed in a space surrounded by the endless track and has a flat portion that makes contact with an inner circumferential surface of at least one of two portions, of the endless track existing between the first pulley and the second pulley , that face each other, wherein the flat portion of the planar member makes contact with the inner circumferential surface of the endless track at a position at the traveling subject side with respect to a virtual straight line (X1) that connects a vertex (A1), at the traveling subject side, in the outer circumferential surface (33a1) of the first pulley and a vertex(B1), at the traveling subject side, in the outer circumferential surface (33b1) of the second pulley , wherein at least part of the outer circumferential surface, of the endless track , that faces the inner circumferential surface being in contact with the flat portion of the planar member is configured such that it makes contact with the traveling subject , characterized in that the endless track is formed in such a way that the hardness of the inner circumferential surface is larger than the hardness of the outer circumferential surface. <EOS>