A method for controlling a work machine, includes: detecting an area present ahead in a traveling direction of a work machine, in which a target traveling speed of the work machine is constant and is lower than a traveling speed at a current point of time; when the area is detected, obtaining a corrected value for correcting the accelerating instruction value; adding the corrected value and an accelerating instruction value for controlling a traveling speed of the work machine obtained based on the target traveling speed to obtain a corrected accelerating instruction value; and outputting the corrected accelerating instruction value to a drive device configured to drive a traveling device in the work machine.