The present invention relates to the field of crushing equipment production, and particularly provides a crushing device for a polystyrene sheet. The crushing device structurally comprises a crushing shell, a crushing mechanism, a driving motor and a control mechanism, and is characterized by further comprising a feeding unit. The feeding unit mainly comprises a feeding shell, a conveying mechanism and longitudinal cutting mechanisms. The feeding shell is arranged at a feeding inlet of the crushing shell, and the conveying mechanism comprises at least two conveying belts, a feeding motor, a driving roller and a driven roller. The conveying belts are parallel to one another and are all in transmission connection to the driving roller and the driven roller. The driving roller is located outside the feeding shell and in transmission connection to the feeding motor. The driven roller is located at the feeding inlet of the crushing shell inside the feeding shell. One of the longitudinal cutting mechanisms is arranged between each two adjacent conveying belts, and both the feeding motor and the longitudinal cutting mechanisms are electrically connected with the control mechanism. Compared with the prior art, the crushing device for the polystyrene sheet has the advantages of desirable crushing effects and no dust pollution.