The photoacoustic spectroscopy (PAS) with piezoelectric transducer was employed to evaluate band gap energies in Zn1-xBexSe mixed crystals of different composition The spectra were measured at 300 K and 90 K using continuos wave excitation. The Jackson-Amer model of photoacoustic effect was applied. The increase of the band-gap energy with increasing Be content is observed. The photoacoustic results are compared with those from photoluminescence spectra.