We report on a detailed experimental study of the electron transport anisotropy in HgTe (013) quantum well of 22 nm width in the directions [100] and [031¯] as the electron density function n. The anisotropy is absent at the minimal electron density near a charge neutrality point. The anisotropy increases with the increase in n and reaches about 10% when the Fermi level is within the first subband H1. There is a sharp increase in the anisotropy (up to 60%) when the Fermi level reaches the second subband E2. We conclude that the first effect is due to the small intra-subband anisotropic interface roughness scattering, and the second one is due to the strongly anisotropic inter-subband roughness scattering, but the microscopical reason for such a strong change in the anisotropy remains unknown.