To stabilize a waterproofing function by additionally providing a chamber surrounding the boundary part of a power source cord and a partition wall at the partition wall on the inside of the housing of a battery charger with the power source cord of an inductive charging system charging the battery of a tooth brush main body and filling this chamber with waterproofing bond.

An inside of a battery charger 2 charging a battery built in a toothbrush main body is partitioned into a large chamber 10 and a small chamber 11 by a partition wall 12 constituting a housing and a chamber 15 surrounding a boundary part of a power source cord 7 and the partition wall 12, namely a supporting member 8 with the cord 7 put through, and the surrounding is additionally provided at the partition wall 12 through which the cord 7 passes. Then the chamber 15 is filled with a waterproofing bond 30, a bottom cover 20 is fitted to a bottom part of the charger 2 and after then, the fitting part is connected by ultrasonic spray coating to make waterproofing structure. Thus, the applying work of the bond 30 is facilitated and the using quantity of the bond 30 is reduced to reduce a cost.