A coil device having a bobbin structure, includes a body section, a first flange section and a second flange section. The body section is positioned between the first flange section and the second flange section in a first horizontal direction. The first flange section includes a first lower base and a first upper portion. The first upper portion extends upwardly from the first lower base. The first upper portion is provided with a first upper edge on which at least one guide recess is formed. The second flange section includes a second lower base and a second upper portion. The second lower base faces the first lower base in the first horizontal direction. The second upper portion extends upwardly from the second lower base. The second upper portion faces the first upper portion in the first horizontal direction with the body section interposed therebetween.