A coil device includes a core including a winding core portion and a flange portion provided in an end portion of the winding core portion in an X-axis direction, a coil portion formed by a first wire and a second wire being wound around the winding core portion, and a first terminal electrode formed on one end side of the flange portion in a Y-axis direction, a first lead portion of the first wire being connected to the first terminal electrode, and a second terminal electrode formed on the other end side of the flange portion in the Y-axis direction, a second lead portion of the second wire being connected to the second terminal electrode. The width of the flange portion along X-axis-direction is different between one end and the other end of the flange portion in the Y-axis-direction.