To provide an electric riding mower which can maintain a fixed mowing height even if there is a swell.

The electric riding mower includes: a mower blade which rotates to mow grass; substantially bowl-shaped mower decks 15 which cover the mower blade from above and sides; a mower motor 20 which is disposed on the mower decks 15 and which is attached to a rotating axis of the mower blade; a main frame 18 which suspends the mower decks 15 on both right and left sides in such a way as rotatable in the vertical direction and which is extended in the direction of advancement; and gauge wheels 23 for detecting a swell on a traveling surface. The respective mower decks 15 are independently rotated along the main frame 18 according to the swell on the traveling surface detected by the gauge wheels 23.