A grass mower is provided with a plurality of rotating shafts (21) passing through a ceiling wall (31) of a mower deck (30) and extending upward, disposed in a side-by-side state； cutting blades (20) respectively linked to the rotating shafts (21) in an internal space of the mower deck (30)； an electric motor (4) mounted at a location to the lateral outside relative to a rotation path of the cutting blades (20) within the mower deck (30), and having an output shaft (41) extending upward； and a power transmission mechanism (7) positioned above the ceiling wall (31) of the mower deck (30), and configured to transmit power from the output shaft (41) to the rotating shafts (21) of the cutting blades (20).
