We study the stochastic four-state sandpile model on the square lattice.The static and dynamical properties of the model are investigated andcompared with the deterministic sandpile model of Bak, Tang, andWiesenfeld [Phys. Rev. Lett. 59 (1987) 381]. The numerical results showthat the stochastic model defines a new universality class with respectto the deterministic sandpile. We also find that the waves in anavalanche are uncorrelated in the stochastic model (in the BTW model,the waves in an avalanche are correlated). The physical origin of thecritical behaviour of the stochastic model being different from that ofthe BTW model is ascribed to the ordering and deterministic property ofthe toppling law in the BTW model.