A coil device includes a coil unit for stowing a coil part, and a heat dissipation unit thermally connected to the coil unit. The heat dissipation unit has a heat dissipation body, a heat dissipation fin movable relative to the heat dissipation body, and a fin drive mechanism for driving the heat dissipation fin. The heat dissipation unit has a heat dissipation configuration in which the heat dissipation fin projects from the heat dissipation body in a direction intersecting a winding axis, and a stowed configuration in which the heat dissipation fin is stowed in the heat dissipation body.