A foot support installed on a floor panel of an operator cab has a rear surface section that rises upward in a rear-to-front direction of the operator cab and an upper surface section that is provided in front of the rear surface section so as to continue therefrom and slopes downward in the rear-to-front direction of the operator cab. A heel position adjusting plate having a heel rest portion is mounted such that the relative distance of the heel rest portion with respect to the foot support is adjustable.