The invention provides a breathing machine and a proportional valve. The proportional valve comprises a shell body and a valve seat. The shell body comprises a cavity body, an inlet, an outlet and a valve port are formed in the valve seat, the shell body is connected with the valve seat in a sealing mode, and the inlet is communicated with the valve port. A coil, a first soft magnet, an armature, a first elastic element and a seal cover plate are arranged inside the shell body. The coil is wound on the outer periphery of the first soft magnet, the first magnet is arranged on an axial first side of the armature, the seal cover plate is connected with an axial second side of the armature, the first elastic element is arranged on the second side of the armature, and the first soft magnet drives the armature to enable the surface of the seal cover plate to contact with or separate from the end face of the valve port. Flow control of the proportional valve is realized through the opening and the closing between the seal cover plate and the end face of the valve port, wherein the opening and the closing are controlled in an electromagnetic mode. Therefore, the aging problem of a seal ring when the seal ring is used for sealing does not exist, and the proportional valve has the advantages of being good in sealing effect, high in response speed, low in cost, convenient to repair, and capable of reducing hysteresis phenomenon.