Provided is a sustained-release microparticle preparation of a human growth hormone which combines biodegradability with sustained-release performance while avoiding the use of an organic solvent as much as possible, allows the sustained-release of a human growth hormone over 3 days or more and reduction in the initial burst release, can contain a human growth hormone at 10% or more, can quantitatively adsorb and encapsulate a human growth hormone at up to 20%, and has excellent dispersion and needle penetration properties. A process for producing the sustained-release microparticle preparation of a human growth hormone is also provided. The sustained-release microparticle preparation comprises a porous apatite derivative, a human growth hormone, and a water-soluble divalent metal compound.