There is provided a sump assembly of a dishwasher. The sump assembly includes a self-cleaning filter assembly having a mesh filter, a sump cover for mounting the self-cleaning filter assembly on a top surface thereof, the sump cover having a filter supporting sleeve extending upward for supporting the self-cleaning filter assembly, a sump case seating on an upper portion of the sump cover to reserve washing water, and a fluid passage guide for discharging the washing water stored in the sump case in a predetermined direction, the fluid passage guide having a washing pump disposed therein.