An electromagnetic switch for an auxiliary rotation starter

In an electromagnetic switch for a sub screw starter according to the present invention, the magnetic bypass core is disposed at a location which is located in an air gap portion in a magnetic circuit, the piston moves through due to a magnetic attractive force by exciting the attracting coil and the holding coil is produced, and which is located in such a manner between the outer periphery of the piston and the inner circumference of the coil bobbin that one end thereof comes to one end of the housing in contact and the other end thereof facing the end of the core by means of an air gap.