An idle speed controller for an internal combustion engine provided with an intake variable valve timing mechanism for varying valve timing and a variable working angle for varying a valve working angle of an intake valve. The controller performs idle speed control. When an advancement failure occurs in the intake variable valve timing mechanism, the controller performs idle-up control to increase the target idle speed. When the valve working angle of the intake variable working angle mechanism is less than a predetermined value, the electronic control unit changes an increase amount of the target idle speed to a lower value if an advancement failure occurs when performing the idle-up as compared to when the valve working angle is greater than the predetermined value.