A method for producing forsterite microparticles having a primary particle size of 1, to 50 nm, as determined through electron microscopy. The method includes spray-drying, in an atmosphere of 50° C. or higher and lower than 300° C., a solution containing a water-soluble magnesium salt and colloidal silica at a mole ratio of magnesium atoms to silicon atoms (Mg/Si) of 2; and subsequently, firing the spray-dried product in air at 800 to 1,000° C.