A power tool comprising: a brushless motor (1; 401) including a rotor (12; 412) configured to rotate; a rectifier circuit configured to rectify an AC voltage; a smoothing capacitor configured to smooth the AC voltage rectified by the rectifier circuit to a pulsating voltage; an inverter circuit configured to perform switching operations to output the pulsating voltage to the brushless motor (1; 401); a deceleration mechanism (9; 109; 209; 309; 409) configured to decelerate a speed of a rotation of the rotor (12; 412) and configured to transmit the rotation to an end tool (4; 404); an elastic member (13; 113; 213; 313; 413) disposed between a driving portion (94; 194; 294; 494) at a rotor side and a driven portion (92; 192; 292) configured to transmit a rotating force to an end tool side, the elastic member (13; 113; 213; 313; 413) being configured to transmit the rotating force of the driving portion (94; 194; 294; 494) to the driven portion (92; 192; 292); a detection portion configured to detect a rotation state of the brushless motor (1; 401); and a control unit configured to detect a rotation speed of the brushless motor (1; 401) based on a detection result of the detection portion and configured to control the switching operations of the inverter circuit based on the detected rotation speed, wherein the control unit is configured to perform a constant-speed control where the rotation speed of the brushless motor (1; 401) is maintained constant until a load applied to the end tool (4; 404) reaches a predetermined load, wherein the elastic member (13; 113; 213; 313; 413) has a degree of hardness so that the elastic member (13; 113; 213; 313; 413) is deformable in a condition where the load less than the predetermined load is applied to the end tool (4; 404), characterized in that each of the driving portion (94; 194; 294; 494) and the driven portion (92; 192; 292) has a contact portion (94A, 95C; 194A) at which the driving portion (94; 194; 294; 494) and the driven portion (92; 192; 292) directly contact with each other in a rotating direction thereof when the elastic member (13; 113; 213; 313; 413) deforms in predetermined amount, due to a second load greater than the predetermined load being applied to the end tool (4; 404), and wherein the control unit is configured to perform an overcurrent protection so that the brushless motor (1;401) is stopped when a third load greater than the second load is applied to the end tool (4; 404). a brushless motor (1; 401) including a rotor (12; 412) configured to rotate; a rectifier circuit configured to rectify an AC voltage; a smoothing capacitor configured to smooth the AC voltage rectified by the rectifier circuit to a pulsating voltage; an inverter circuit configured to perform switching operations to output the pulsating voltage to the brushless motor (1; 401); a deceleration mechanism (9; 109; 209; 309; 409) configured to decelerate a speed of a rotation of the rotor (12; 412) and configured to transmit the rotation to an end tool (4; 404); an elastic member (13; 113; 213; 313; 413) disposed between a driving portion (94; 194; 294; 494) at a rotor side and a driven portion (92; 192; 292) configured to transmit a rotating force to an end tool side, the elastic member (13; 113; 213; 313; 413) being configured to transmit the rotating force of the driving portion (94; 194; 294; 494) to the driven portion (92; 192; 292); a detection portion configured to detect a rotation state of the brushless motor (1; 401); and a control unit configured to detect a rotation speed of the brushless motor (1; 401) based on a detection result of the detection portion and configured to control the switching operations of the inverter circuit based on the detected rotation speed, wherein the control unit is configured to perform a constant-speed control where the rotation speed of the brushless motor (1; 401) is maintained constant until a load applied to the end tool (4; 404) reaches a predetermined load, wherein the elastic member (13; 113; 213; 313; 413) has a degree of hardness so that the elastic member (13; 113; 213; 313; 413) is deformable in a condition where the load less than the predetermined load is applied to the end tool (4; 404), characterized in that each of the driving portion (94; 194; 294; 494) and the driven portion (92; 192; 292) has a contact portion (94A, 95C; 194A) at which the driving portion (94; 194; 294; 494) and the driven portion (92; 192; 292) directly contact with each other in a rotating direction thereof when the elastic member (13; 113; 213; 313; 413) deforms in predetermined amount, due to a second load greater than the predetermined load being applied to the end tool (4; 404), and wherein the control unit is configured to perform an overcurrent protection so that the brushless motor (1;401) is stopped when a third load greater than the second load is applied to the end tool (4; 404).