A coil device includes a board, a first pattern formed on one surface of the board, and a second pattern formed on the other surface of the board. At least one pattern via electrically connects the first pattern and the second pattern to each other. A via region, corresponding to a region in which the pattern via is formed in the first pattern, includes n first conducting wires (where n is a natural number of 1 or more). At least a portion of the first pattern, excluding the via region in the first pattern, includes m first conducting wires (where m is greater than n and is a natural number of 2 or more).