Brake device for bicycle

The invention discloses a brake device for a bicycle, which comprises a crank, a connecting rod, a slide block, an air cylinder, a back wheel shaft of the bicycle and a brake wire, wherein one end of the crank is fastened on the back wheel shaft of the bicycle, the other end of the crank is connected with the connecting rod, the other end of the connecting rod is connected with the slide block, the front end of the air cylinder is provided with a first air cylinder cover, a third air cylinder cover and a second air cylinder cover are sequentially arranged at the back end of the air cylinder and are connected through a reset spring, an exhaust hole of the first air cylinder cover and two holes of the first air cylinder cover are arranged in the first air cylinder cover, an exhaust hole of the second air cylinder cover is arranged in the second air cylinder cover, an exhaust hole of the third air cylinder cover is arranged in the third air cylinder cover, a piston is arranged in the air cylinder and is connected with the slide block through a piston rod, the piston rod passes through the two holes of the first air cylinder cover, and the third air cylinder cover is connected with the brake wire. The brake device for the bicycle solves the abrasion problem of the traditional brake rubber, safety and reliability are realized, the appearance is more novel, and the brake device for the bicycle has the advantages of ingenious design, good use effect and the like.