The invention relates to a wheelchair having an automatic brake function. The wheelchair comprises a main body as well as wheels, a seat, armrests, a storage battery, brake mechanisms and speed-measuring mechanisms, wherein each brake mechanism comprises a brake sheet, a brake caliper, a piston, a hydraulic pipe, a brake master cylinder, a supporting rod, a pull wire, a wire coil and a motor; and each speed-measuring mechanism comprises a first connecting rod, a second connecting rod, a spring, an iron block and an electromagnet. The wheelchair having the automatic brake function is elaborate in design and reasonable in structure; by squeezing the brake master cylinders by virtue of the supporting rods, friction brake is achieved between the pistons and the brake sheets; in the case that the wheelchair moves too fast, the motors can be automatically turned on by virtue of the speed-measuring mechanisms so as to draw the supporting rods to achieve brake; and in order to prevent falling which easily occurs in the case of emergency brake, the iron blocks can be adsorbed by virtue of the electromagnets, so that brakes are loosened by virtue of the speed-measuring mechanisms, and subsequently, the speed of the wheelchair is slowly reduced.