A brake device for a motor vehicle seat, comprising: a brake assembly including a housing, a pinion shaft, a braking component (14, 15, 16, 17), and a drive wheel that are structured to be self-held in an assembled state by mechanical interaction thereamong; a tooth assembly including a holder plate and a tooth plate that are structured to be self-held in an assembled state by mechanical interaction therebetween; and a lever assembly including an input lever, a cover, a coil spring, and a lever bracket that are structured to be self-held in an assembled state by mechanical interaction thereamong, wherein the brake assembly, the tooth assembly, and the lever assembly are arranged and assembled together in an axial direction; wherein: the brake assembly is structured as a braking section to resist an external torque inputted through the pinion shaft; the tooth assembly and the lever assembly are structured as an operating section to operate the pinion shaft; the pinion shaft extends through the drive wheel, the holder plate, and the input lever, and is supported rotatably with respect to the holder plate and the input lever; the braking component (14, 15, 16, 17) and the drive wheel are mounted in the housing; the drive wheel is structured to rotate along with the pinion shaft, and includes an internal tooth part; the holder plate is structured to frictionally resist rotation of the drive wheel, and includes a first support part; the tooth plate is rotatably supported by the first support part of the holder plate, and includes a pair of external tooth parts each of which is structured to engage with the internal tooth part of the drive wheel; the input lever includes a second support part structured to engage with the tooth plate, wherein the second support part is offset from the first support part of the holder plate; the cover is coupled with the housing to contain the holder plate, the tooth plate, and the input lever; the coil spring is structured to bias the input lever toward a neutral position; and the lever bracket is disposed outside the cover, and coupled with the input lever, characterized in that the holder plate includes a holding part structured to prevent the tooth plate from being released from the first support part. a brake assembly including a housing, a pinion shaft, a braking component (14, 15, 16, 17), and a drive wheel that are structured to be self-held in an assembled state by mechanical interaction thereamong; a tooth assembly including a holder plate and a tooth plate that are structured to be self-held in an assembled state by mechanical interaction therebetween; and a lever assembly including an input lever, a cover, a coil spring, and a lever bracket that are structured to be self-held in an assembled state by mechanical interaction thereamong, wherein the brake assembly, the tooth assembly, and the lever assembly are arranged and assembled together in an axial direction; the brake assembly is structured as a braking section to resist an external torque inputted through the pinion shaft; the tooth assembly and the lever assembly are structured as an operating section to operate the pinion shaft; the pinion shaft extends through the drive wheel, the holder plate, and the input lever, and is supported rotatably with respect to the holder plate and the input lever; the braking component (14, 15, 16, 17) and the drive wheel are mounted in the housing; the drive wheel is structured to rotate along with the pinion shaft, and includes an internal tooth part; the holder plate is structured to frictionally resist rotation of the drive wheel, and includes a first support part; the tooth plate is rotatably supported by the first support part of the holder plate, and includes a pair of external tooth parts each of which is structured to engage with the internal tooth part of the drive wheel; the input lever includes a second support part structured to engage with the tooth plate, wherein the second support part is offset from the first support part of the holder plate; the cover is coupled with the housing to contain the holder plate, the tooth plate, and the input lever; the coil spring is structured to bias the input lever toward a neutral position; and the lever bracket is disposed outside the cover, and coupled with the input lever,