A rotary impact tool can be used continuously for fastening a plurality of fastening members such as screws, bolts or nuts in tight fastening mode. The rotary impact tool comprises a rotary driving mechanism including a motor for rotating a driving shaft, a hammer engaged with the driving shaft, an output shaft to which a driving force is applied by impact blow of the hammer, a main switch operated by a user for controlling fastening operation, and a controller for controlling on and off of the motor. The controller has a normal fastening mode and a tight fastening mode, and a tight fastening mode setting switch used for setting the tight fastening mode is further comprised. When the tight fastening mode setting switch is switched on, the controller continuously drives the rotary driving mechanism so as to perform tight fastening operation continuously.