A box-shaped beach-cleaning trailer is configured to be loaded with, and collectively carry beach-cleaning equipment and a litter collection station. The beach-cleaning equipment are towed by a vehicle to collect litter on the sands. The litter collected by the beach-cleaning equipment is collected in the litter collection station. The trailer includes a pair of rail members disposed on upper edges of the respective opposite side wall portions such that the rail members face each other with an opening therebetween. A sieve unit is detachably mounted on the rail members, and is configured to move a back-and-forth direction along the rail members. The sieve unit is moved in a back-and-forth direction manually; or by using a driving mechanism including a drive wheel, a driven wheel, and a connecting rod arranged between the sieve unit and the driven wheel, for separating colleted litter of various sizes from sand.