The invention discloses a braking device for a railcar. The braking device is arranged on a wheel carrier of a wheel set of the railcar. The braking device for the railcar comprises a braking frame arranged on the wheel carrier, wherein the braking frame comprises a rail sleeve capable of half-encircling a steel rail; a T-shaped groove is formed in the rail sleeve; brakes fixedly connected to the rail sleeve are arranged between the inner top, the left side part, the right side part, the left bottom and the right bottom of the rail sleeve and the steel rail. The steel rail is half-encircled by the T-shaped groove of the rail sleeve, the T-shaped groove turns to the bottom side of the steel rail, the brakes are arranged on the inner side of the rail sleeve, and are positioned between the rail sleeve and the steel rail, and gaps are formed between the brakes and the steel rail when the railcar normally runs, and are pneumatically expanded to drive the brakes to be closely attached to the steel rail to encircle the steel rail from the top, the left side part, the right side part, the left bottom and the right bottom in case of emergency braking, so that the railcar is synchronously braked under equal pressure in five gears and five points in emergency, derailment and tailgating are avoided, damage to the steel rail at low gears is avoided, safety is ensured by sacrificing the steel rail at high gears, and higher reliability of braking within a visual distance is achieved.