The invention discloses a size-adjustable garbage can. The size-adjustable garbage can is characterized by comprising a garbage can body, a contraction ring, a telescopic piece and a hinge, a plurality of supporting pieces are arranged on the garbage can body at equal intervals, height adjusting holes are formed in the supporting pieces, telescopic connecting pieces are arranged on the contractionring, the number of the telescopic connecting pieces is two, moreover, the two telescopic connecting pieces are symmetrically arranged, an adjusting knob is arranged on each telescopic connecting piece, a plurality of diameter adjusting holes are formed in the contraction ring, the top of the telescopic piece is connected with the hinge, the hinge is connected with the contraction ring through screws and the diameter adjusting holes, telescopic connecting blocks are arranged at the lower part of the telescopic piece, and the telescopic connecting blocks are movably connected with the supporting pieces through the height adjusting holes. According to the garbage can, the structural design is reasonable, the diameter of the garbage can and the height of the garbage can be adjusted, the garbage can is capable of being applied to plastic garbage bags with different lengths and sizes, and the garbage can is convenient for people to use.