Provided is an electromagnetic switch device for starters that is easy to manufacture and is small in size while including a built-in auxiliary relay. This electromagnetic switch device (17) for a starter comprises: a main contact chamber (34) in which a pair of main fixed contacts (20) is arranged, and that forms a space in which a main movable contact 22 can move; a sub-contact chamber 35 in which a pair of sub-fixed cores (A) (60), (B) (61) is arranged, and that forms a space in which a sub-movable contact (29) can move; and a cylindrical terminal block (37) on which the main contact chamber (34) and a sub-coil (32) are arranged such that the sub-coil (32) and the main contact chamber (34) are adjacent to one another in the radial direction across a partition wall (36) that separates the sub-coil and the main contact chamber.