A polyhydroxyalkanoate containing in a molecule at least one unit represented by the chemical formula (1). The polyhydroxyalkanoate is a biodegradable plastic with enhanced melt-processability and exhibits excellent charging stability, high chargeability, and enhanced dispersibility when used as a charge control agent of a toner in an electrophotographic process. ##STR00001## (R denotes -A.sub.1(--SO.sub.2R.sub.1).sub.x. R.sub.1 is selected from OH, a halogen atom, ONa, OK, and OR.sub.1a. R.sub.1a and A.sub.1 are selected from a substituted or unsubstituted aliphatic hydrocarbon structure, a substituted or unsubstituted aromatic ring structure, and a substituted or unsubstituted heterocyclic structure. Further, m and x are integers selected from 1 to 8, and when two or more units exist, each of R, R.sub.1R.sub.1a, A.sub.1, m, and x is defined as above independently for each of the units.)