A brake chamber provided with a configuration connecting a housing, which forms an accommodation space for a push plate, and a cylinder, in which a pushrod is accommodated. In order to prevent problems caused by the intrusion of foreign matter into the housing resulting in insufficient strength at the position where the housing and the cylinder are connected, while inhibiting an increase in costs, a brake chamber (1) is provided with: a rod portion (22), in which a pushrod (2) is made to advance towards a brake device by a piston action in a cylinder (17) by means of compressed air pressure; and a dust boot (29), which prevents the intrusion of foreign matter such as mud into the cylinder (17). A sealing portion (29c) is formed on the dust boot (29) and acts to prevent the intrusion of foreign matter to the connection portion of a cup (16) and the cylinder (17) by being in elastic contact with the inner peripheral surface (16b) of the cup (16).
