A screwdriver includes a handle, a shaft, a torque-transmitting unit and a torque-adjusting unit. The shaft is partially inserted in the handle. The torque-transmitting unit is located in the handle and operable to transmit an adjustable maximum value of torque to the shaft from the handle. The torque-adjusting unit is partially located in the handle, connected to the torque-transmitting unit, and operable to adjust the adjustable maximum value of torque.