The dynamics of the quantum wave dark matter (ψDM) can be described by the Schrödinger-Poisson equation. We numerically solve it in hydrodynamic form by the Lax–Wendroff method. The accuracy of the program is tested with several analytic solutions, e.g., plane wave, perturbation wave, Gaussian wave packet, standing wave, vortex pairs. We encounter some numerical problems so that we improve the algorithm by adding numerical diffusion, slightly changing the mathematical form, and regularizing the flux term.