To prevent the hand of an operator from touching the cutting edge of a dental treatment instrument when the instrument is taken-out from an instrument holder and also to prevent a drawn-out instrument hose from touching the edge of the adjacent instrument.

The placement surface of an instrument placing part 7a in the instrument holder 7 is inclined forward and also downward in the drawing direction of the instrument 5. In this case, a height for grasping the instrument by an operator differs from the height position of the blade of the instrument 5 when the instrument 5 is taken-out from the instrument holder 7 in an operation. Then the hand of the operator is prevented from touching the blade of the instrument and also the instrument hose of the drawn-out instrument is not brought into contact with the edged tool of the adjacent instrument.