A riding grass-mower, including a mower unit (1000) which has a mower deck (1100) such that an upper face is constituted with a mower deck top-plate member (1200) and a lower face is opened, and is configured to mow a grass, wherein the mower unit (1000), in an interior part of the mower deck (1100), has: a pair of mowing blades (1110, 1120) which are provided side by side in a left-and-right direction, and are configured to mow the grass； and a mowed-grass guiding passage (1400) which is provided at a mower central part in the left-and-right direction, and is configured to guide the mowed grass, and an air intake hole (1210) is provided at such a portion of the mower deck top-plate member (1200) as is placed over the mowed-grass guiding passage (1400).
