A crawler device comprising: front and rear wheels (5; 70; 80); and a crawler belt (10; 10') wrapped around the front and rear wheels (5; 70; 80); wherein: the crawler belt (10; 10') comprises: (a) an endless belt main body; (b) a multitude of tread lugs formed in an outer periphery of the belt main body such that the tread lugs are spaced from one another in a peripheral direction; and (c) a pair of disengagement prevention sections formed in the belt main body along the peripheral direction such that the pair of disengagement prevention sections are spaced from each other in a width direction of the belt main body; and the pair of disengagement prevention sections can be protruded inward in a radial direction of the crawler belt (10; 10') so as to be engageable with opposite side surfaces of the wheels (5; 70; 80) for preventing the crawler belt (10; 10') from being disengaged from the wheels (5; 70; 80), wherein each of the disengagement prevention sections comprises a multitude of rib segments (13a; 92) arranged along the peripheral direction spaced from one another, the rib segments (13a; 92) extending in the peripheral direction; the rib segments (13a; 92) are disposed at positions corresponding to positions of the tread lugs in the peripheral direction; a multitude of first engagement protrusions (42; 74; 82b) are formed in an outer periphery of the wheels (5; 70; 80) such that the first engagement protrusions (42; 74; 82b) are spaced from one another in the peripheral direction; a multitude of second engagement protrusions engageable with the first engagement protrusions (42; 74; 82b) are formed in the inner periphery of the belt main body of the crawler belt (10; 10') such that the second engagement protrusions are spaced from one another in the peripheral direction; and characterized in that plays in the peripheral direction are provided between the first engagement protrusions (42; 74; 82b) and the second engagement protrusions, and that the plays in the peripheral direction between the first engagement protrusions (42; 74; 82b) and the second engagement protrusions are of a size from three to eight times dimensions of the first engagement protrusions (42; 74; 82b) in the peripheral direction. front and rear wheels (5; 70; 80); and a crawler belt (10; 10') wrapped around the front and rear wheels (5; 70; 80); the crawler belt (10; 10') comprises: (a) an endless belt main body; (b) a multitude of tread lugs formed in an outer periphery of the belt main body such that the tread lugs are spaced from one another in a peripheral direction; and (c) a pair of disengagement prevention sections formed in the belt main body along the peripheral direction such that the pair of disengagement prevention sections are spaced from each other in a width direction of the belt main body; and (a) an endless belt main body; (b) a multitude of tread lugs formed in an outer periphery of the belt main body such that the tread lugs are spaced from one another in a peripheral direction; and (c) a pair of disengagement prevention sections formed in the belt main body along the peripheral direction such that the pair of disengagement prevention sections are spaced from each other in a width direction of the belt main body; and the pair of disengagement prevention sections can be protruded inward in a radial direction of the crawler belt (10; 10') so as to be engageable with opposite side surfaces of the wheels (5; 70; 80) for preventing the crawler belt (10; 10') from being disengaged from the wheels (5; 70; 80), wherein each of the disengagement prevention sections comprises a multitude of rib segments (13a; 92) arranged along the peripheral direction spaced from one another, the rib segments (13a; 92) extending in the peripheral direction; the rib segments (13a; 92) are disposed at positions corresponding to positions of the tread lugs in the peripheral direction; a multitude of first engagement protrusions (42; 74; 82b) are formed in an outer periphery of the wheels (5; 70; 80) such that the first engagement protrusions (42; 74; 82b) are spaced from one another in the peripheral direction; a multitude of second engagement protrusions engageable with the first engagement protrusions (42; 74; 82b) are formed in the inner periphery of the belt main body of the crawler belt (10; 10') such that the second engagement protrusions are spaced from one another in the peripheral direction; and characterized in that plays in the peripheral direction are provided between the first engagement protrusions (42; 74; 82b) and the second engagement protrusions, and that the plays in the peripheral direction between the first engagement protrusions (42; 74; 82b) and the second engagement protrusions are of a size from three to eight times dimensions of the first engagement protrusions (42; 74; 82b) in the peripheral direction.