An object is to provide a control device of a dental handpiece that is able to prevent giving a shock to the operator having the dental handpiece and the patient of treatment subject and also that is able to reduce the load onto the motor and to suppress heat generation thereof. The rotational direction of a motor 20 of a dental handpiece is switched at every certain time. At this time, before the rotational direction of the motor 20 is switched through switching of a relay 17, voltage to be applied to the motor 20 is reduced. It is thereby prevented that a large current flows into the motor 20 when the relay 17 is switched, and also that a large rotation torque is applied to a cutting tool rotationally driven by the motor 20.本發明之目的,係在於提供一種:能夠防止對於握持齒科用手持電鑽之施術者和治療對象之患者賦予衝擊,並減輕馬達之負載,且能夠對於發熱作抑制之齒科用手持電鑽之控制裝置。將齒科用手持電鑽之馬達(20)的旋轉方向,在每經過一定時間時作切換。此時,在切換中繼器(17)並將馬達(20)之旋轉方向作切換前,係將施加於馬達(20)處之電壓降低。藉由此,能夠防止在切換中繼器(17)而對馬達(20)流動大電流,並防止對於經由馬達(20)所旋轉驅動之切削工具施加大的旋轉轉矩。
