Coils (220, 320) are respectively arranged on a front side and a rear side of a planned conveyance plane (CP). Non-edge cores (211, 311) and edge cores (212-213, 312-313) are arranged with respect to the coils (220, 320). The non-edge cores (211, 311) are so-called T-shaped cores, and arranged at center regions in an x-axis direction. Two edge cores (212-213, 312-313) are so-called E-shaped cores, and arranged on both sides in the x-axis direction of the non-edge cores (211, 311), respectively. An interval between upstream-side leg portions (2122, 3122) and downstream-side leg portions (2123, 3123) provided to the edge cores (212, 313) and the planned conveyance plane (CP), is shorter than an interval between parts of the non-edge cores (211, 311) except for center leg portions (2111, 3111) thereof and the planned conveyance plane (CP).