A filter device includes a plurality of coils of which central axes are spaced apart from one another and in parallel to one another and a plurality of ground members spaced apart from one another and extending in parallel to the central axes of the coils outside of the coils. Each of the coils is spaced apart from another coil closest thereto by a first distance. Each of the ground members is spaced apart from a coil closest thereto by a second distance. The number of ground members spaced apart from each of the coils by the second distance is the same.