The present invention has a high open cell rate at high magnification, excellent environmental compatibility and biodegradability, to provide a method for producing extruded foam poly (3-hydroxyalkanoate) (P3HA) produced from a microorganism and an object, to create the mixture was melt-kneaded P3HA and volatile foaming agent, a process for the preparation of the extruded foam obtained by extruding the low pressure region the mixture through the forming die, the P3HA a volatile blowing agent production of P3HA resin extruded foam, wherein the mixture of the resin at the time of extruding from the extruder temperature to (temperature of the resin as measured by the thermocouple in an extruder discharge port) is in the range represented by the following formula to provide a method.
Tc-20 ≦ To (℃) ≦ Tc + 20
(Where, Tc = (Tg + Tm) / 2, Tg is a glass transition temperature of the P3HA, Tm denotes a melting point of P3HA.)