Provided is a brake device whereby stress during a brake operation is suppressed. A brake device 140 is provided with: a rotary member 141 for synchronously rotating with a wheel 131, the rotary member 141 being provided with a round external peripheral part arranged concentrically with the wheel 131, and a plurality of engaging teeth 141a protruding radially from the external peripheral part； an engaging member 142 retained in movable fashion on a frame part 133 of a wheelchair 100, the engaging member 142 being provided with an engaging projection 142a for engaging with the engaging teeth 141a, the engaging projection 142a being accommodated in grooves 141b between the plurality of engaging teeth 141a of the rotary member 141, and the engaging member 142 shifting between a first position whereby the engaging projection 142a is positioned outside the grooves 141b and a second position where at least a portion of the engaging projection 142a is positioned inside a groove 141b； an urging member 146 for urging the engaging member 142 to one of the first position and the second position； and a lock part 145 for maintaining the engaging member 142 in the other of the first position and the second position.
