In culturing a poly(3-hydroxyalkanoate)-producing microorganism, an oil A and an oil B are used as the carbon source. The proportion of the oil B to the total amount of the oils A and B used during the entire course of the culturing is 10 wt% or more. The oil A is the total oil used until the amount of the poly(3-hydroxyalkanoate) accumulated in the poly(3-hydroxyalkanoate)-producing microorganism reaches 16 wt%, and the average unsaturated fatty acid content in constituent fatty acids is from 25 wt% to less than 75 wt% in the total oil A. The unsaturated fatty acid content in constituent fatty acids in the oil B is higher than the average unsaturated fatty acid content in the total oil A.