A power tool (11A; 11B) comprising: a rotational force generating device having a rotational drive shaft; and a rotational driven shaft (36; 36B; 36C) coupled to the rotational drive shaft via a transmission mechanism, so that the rotation of the rotational drive shaft is transmitted to the rotational driven shaft (36; 36B; 36C) via the transmission mechanism, the rotational driven shaft (36; 36B; 36C) being a separate member from the rotational drive shaft; characterized in that the rotational driven shaft (36; 36B; 36C) is rotatably supported by at least three bearings (37, 381, 382; 37B, 381B, 382B; 371C, 372C, 381C, 382C), the power tool further comprises a tool main body (13A; 13B) comprising a gear housing and a motor housing, wherein the rotational force generating device is disposed in the motor housing and the rotational driven shaft is disposed in the gear housing and the at least three bearings (37, 381, 382) are mounted to the gear housing, or comprising a motor housing and the rotational force generating device and the rotational driven shaft (36B; 36C) are disposed in the motor housing and the at least three bearings (37B, 381B, 382B; 371C, 372C, 381C, 382C) are mounted to the motor housing, and the power tool further comprises a machining tool (14; 14B) for machining a workpiece, wherein the machining tool (14; 14B) is mounted to a mount portion of the rotational driven shaft (36; 36B; 36C), and two (381, 382; 381B, 382B; 381C, 382C) of the at least three bearings are arranged side by side on a side of a portion of the rotational driven shaft where the machining tool is attached. a rotational force generating device having a rotational drive shaft; and a rotational driven shaft (36; 36B; 36C) coupled to the rotational drive shaft via a transmission mechanism, so that the rotation of the rotational drive shaft is transmitted to the rotational driven shaft (36; 36B; 36C) via the transmission mechanism, the rotational driven shaft (36; 36B; 36C) being a separate member from the rotational drive shaft; characterized in that the rotational driven shaft (36; 36B; 36C) is rotatably supported by at least three bearings (37, 381, 382; 37B, 381B, 382B; 371C, 372C, 381C, 382C), the power tool further comprises a tool main body (13A; 13B) comprising a gear housing and a motor housing, wherein the rotational force generating device is disposed in the motor housing and the rotational driven shaft is disposed in the gear housing and the at least three bearings (37, 381, 382) are mounted to the gear housing, or comprising a motor housing and the rotational force generating device and the rotational driven shaft (36B; 36C) are disposed in the motor housing and the at least three bearings (37B, 381B, 382B; 371C, 372C, 381C, 382C) are mounted to the motor housing, and the power tool further comprises a machining tool (14; 14B) for machining a workpiece, wherein the machining tool (14; 14B) is mounted to a mount portion of the rotational driven shaft (36; 36B; 36C), and two (381, 382; 381B, 382B; 381C, 382C) of the at least three bearings are arranged side by side on a side of a portion of the rotational driven shaft where the machining tool is attached.