To provide a heat storage material from which following effects (1)-(7) are expected, namely, (1) downsizing of a tank and an apparatus, (2) adaptability to a wide environmental temperature range by combination of materials or the like, (3) easy adjustment of heat storage capacity by simple addition of units, (4) a large unit heat storage amount, (5) excellent heat transfer performance, (6) low-cost and economical, and (7) lightweight and without corrosion.

A latent heat storage body: is a rectangular or square matrix structural body of which the capsule shell of a matrix type heat storage capsule body (1) is an injection molding formed of an impermeable synthetic resin or metallic aluminum (1a), and which has a plate-like shape requiring a smooth flat surface, and which has mutually independent square or circular hollow layers with various diameters; and is a plate-shaped matrix-structure (type) latent heat storage capsule body of which the inside of the matrix space is subjected to basic maintenance of functions of phase separation prevention, supercooling prevention, change of transition temperature, and thermal conduction acceleration, and of which the inside of the matrix space is filled with an electrolyte hydrate or a hydrocarbon compound (1c) exhibiting a phase change of solidification/liquefaction inherent to a substance and sealed.