A PHA copolymer which is slowly crystallized is improved in crystallization speed to improve the melt workability of the PHA copolymer in working such as injection molding, film molding, blow molding, fiber spinning, extrusion foaming or bead foaming, thereby improving the resultant articles in productivity. A method for the improvement is a method for producing a PHA mixture, including the step of culturing a microorganism having both of a gene encoding a PHA synthase that synthesizes a copolymer PHA (A) and that is derived from the genus Aeromonas, and a gene encoding a PHA synthase that synthesizes a PHA (B) different in melting point from the copolymer PHA (A) by 10° C. or more to produce, in a cell of the microorganism, two or more PHAs different in melting point from one another by 10° C. or more simultaneously.