To allow a user to connect a connection terminal installed on an instrument hose side to any of a plurality of connection terminals installed on a unit side with a one-touch operation and also to a desired connection terminal among the unit side connection terminals.

The instrument hose 9 has the connection terminal 12 that can be connected detachably with a one-touch operation to the connection terminals 20 fixed on a dental treatment unit 2 side. A light irradiation and reflected light detection device for emitting light and for detecting reflection of the emitted light is installed on the peripheral surface of the connection terminal 20 along a predetermined peripheral length l. The peripheral surface of the connection terminal 12 on the instrument hose 9 side has a notch 40 having a peripheral length of lx in a position corresponding to a part of the predetermined peripheral length l where the light irradiation and reflected light detection device is installed. Because the peripheral lengths lx of the notches 40 differ according to the types of the instruments, the type of the instrument connected to the unit body is distinguished by differences of reflected light.