The present invention provides a method of effectively producing polyhydroxyalkanoate having an aromatic substituted residue in its monomer unit. In the method of producing polyhydroxyalkanoate by using microorganisms, microorganisms capable of producing polyhydroxyalkanoate are cultured in a culture medium containing at least one starting compound selected from the group consisting of substituted alkanes represented by formula (1) to produce polyhydroxyalkanoate having, in its molecule, at least one unit selected from the group consisting of 3-hydroxy-substituted alkanoate units represented by formula (2): R--(CH.sub.2).sub.n--CH.sub.2--CH.sub.2--CH.sub.3 (1) wherein R represents a residue containing a substituted aromatic ring, and n represents any integer of 1 to 8; ##STR00001## wherein R represents a residue containing a substituted aromatic ring, and n represents any integer of 1 to 8. In formulas (1) and (2), a residue R is as described in the specification.