PURPOSE: To prepare the subject microcapsule which is difficultly broken underwater and can transport heat without fail.

CONSTITUTION: This microcapsule for heat storage, composed of a core substance comprising a paraffin and a capsule wall comprising calcium silicate and surrounding the core substance, is produced by dispersing a paraffin in an aqueous sodium silicate solution to form an O/W dispersion, dispersing the O/W dispersion in an organic solvent to form an (O/W)/O dispersion and pouring an aqueous calcium chloride solution into the (O/W)/O dispersion to form an ((O/W)/O)/W dispersion, whereupon the calcium chloride dissolved in the outermost aqueous phase diffuses into the innermost aqueous phase and reacts with sodium silicate.