A pickup coil includes a sensing unit having an iron core, a permanent magnet magnetically coupled to a rear end position of the iron core, and a coil for sensing a change of magnetic flux occurring in the iron core; and a supporting frame member. The sensing unit is molded with a cup-shaped resin case. The sensing unit is integrally molded with the supporting frame member and is mounted on a mounting object via the supporting frame member. A plurality of weight units for adjusting a characteristic frequency of the coil is stored in a weight storage section formed inside the resin case at a position spaced away from the supporting frame member. The weight storage section is sized such that one or more weight units are accommodated therein.