Ferroelastic domain boundaries in semiconductor bismuth vanadate, BiVO4, are examined using second harmonic generation microscopy. Although the bulk is centrosymmetric, domain boundaries produce homogeneous second harmonic (SH) signals. The polarization dependences of SH intensities exhibit strong anisotropy compatible with the polar symmetry m. The present results are compared with the experimental results of other ferroelastics we have observed so far. Unlike other ferroelastic materials, the directions of the SH maxima are in the same direction for all domain boundaries.