Poly(butylene, adipate) (PBA) exhibits the two types of crystal modification, the alpha and beta forms, depending, on the sample preparation conditions. They show the different degree of biodegradability. A majority of papers published so far reported that the phase transition from the beta-form to the alpha-form occurs as the direct solid-to-solid process when the sample is heated up to the'high temperature of around 55 degrees C. We have reinvestigated this beta-to-alpha phase transition by performing the temperature-jump time-resolved measurement of the FTIR, WAXD, and SAXS measurements. This transition has been found to be not a solid-to-solid phase transition but the combined phenomena of the melting of the beta-phase followed by the recrystallization to the high-temperature alpha-phase.