A magnetic circuit for a speaker device includes a yoke having a pole piece main body formed into a cylindrical shape or a hollow cylindrical column shape, and a flange part provided on an outer side thereof, a magnet arranged on the flange part, a plate arranged on the magnet, and an annular T-shape forming member arranged on the pole piece main body. A magnetic gap is formed between an inner peripheral wall of the plate and an outer peripheral wall of the T-shape forming member. A configuration formed by combining the T-shape forming member and the pole piece main body forms a T-shaped pole piece.