In a method for crystallising plastic granules with a tendency to conglutinate, in particular PET and PU granules, the granules are subjected to vibratory excitation in a vibrating trough (1) transversely to the direction of longitudinal extension of the vibrating trough (1), at around their reaction temperature. The flow of granules follows a spiral path through the trough, achieving a narrow dwell time spectrum and a homogenous temperature gradient for the granules. Conglutination is also reliably prevented.