To easily and surely perform charging operation, while sustaining desired waterproofness and dustproofness effectively by charging a secondary battery through electromagnetic coupling under a state, where a tool holder incorporating the secondary is positioned relative to a power supply system.

A tool holder 12 is held by fitting the shank part 18 in the tapered hole 84 at a stand section 76, constituting a power supply mechanism 16. In this case, the power-receiving part 66 of the tool holder 12 is matched with a power-transmitting part 74 at the stand section 76 and a first ferromagnetic body 64 is brought into right contact with a second ferromagnetic body 72 through the repelling force of a spring 80. When high-frequency power is fed to a second winding coil, high-frequency power is induced in a first winding coil, coupled magnetically therewith and converted through a rectifier circuit into a DC power, which is fed through a smoothing circuit to a secondary battery 14. According to the arrangement, charging work of the secondary battery 14 is effected quickly and effectively by simply mounting the tool holder 12 on the stand side.