To provide a work tool capable of suppress temperature rise in a motor or a switching element. The work tool includes: a motor; a switching element switchable between an ON-state and an OFF-state, the switching element allowing a current to flow through the motor during the ON-state, the switching element prohibiting a current from flowing through the motor during the OFF-state; target rotation number setting means for setting a target rotation number of the motor; rotation number controlling means for controlling the motor such that the rotation number thereof is brought in coincidence with the target rotation number by changing an ON-duration, during which the switching element is in the ON-state, in one switching period of the switching element; and temperature detecting means for detecting at least one of a temperature of the motor and a temperature of the switching element. The rotation number controlling means is capable of setting an upper limit with respect to the ON-duration on the basis of the temperature detected by the temperature detecting means and changes the ON-duration within a range not more than the upper limit.