The invention provides a particulate construct comprising a polyhydroxyalkanoate to serve as microcapsules containing a drug, and serving a slow releasing preparation not associated with a practically unacceptable initial burst release but showing a practically acceptable zero-order release for a certain period and a producing method for such particulate construct, and a slow releasing preparation of a high drug content capable of stably incorporating the drug in the particulate construct such as microcapsules, and a producing method for such preparation.