A rubber composition for vulcanization molding which can be manufactured into a rubber product with good dimensional stability, good appearance and sufficiently light weight, a process for manufacturing the same, and applications thereof. A rubber composition for vulcanization molding containing hollow particles and a base rubber, wherein the hollow particles are composed of a thermoplastic resin shell and a thermally vaporizable blowing agent encapsulated therein and have a specified further expansion ratio, and the base rubber has a Mooney viscosity ML (1+4) ranging from 5 to 90 at 100° C. Also disclosed is a process for manufacturing the rubber composition, hollow particles used for manufacturing the rubber composition, a masterbatch including the hollow particles and a rubber product manufactured from the rubber composition.