The invention discloses a plastic crusher. The plastic crusher comprises a shell, a crushing mechanism and a transmission mechanism, wherein the crushing mechanism and the transmission mechanism are arranged in the shell. A turnover platform is arranged below a cutoff mechanism. One side of the turnover platform is hinged to the inner wall of the shell, and the turnover platform has a horizontal state and a downward inclination station. A feeding opening is formed in the position, located above the turnover platform, of the outer top face of the shell. A discharging opening is formed in the bottom of the shell. Cutting knives and a baffle are arranged at the positions, located on the two sides of the feeding opening, in the shell, and the cutting knife can stretch and contract in a reciprocating manner in the direction of the baffle. The crushing mechanism comprises multiple roller shafts arranged in the horizontal direction, the side walls between every two adjacent roller shafts areengaged, crushing knives are arranged at the same ends of the multiple roller shafts, and any one roller shaft is connected to the transmission mechanism. The plastic crusher can crush waste plastic efficiently and fast.