Rapidly-solidified ribbons of B2 TiCo were produced by a twin-roll method. Some of the ribbons were annealed at 973K for 12h in a vacuum. It is confirmed by XRD that the as-spun ribbons already have the B2 structure. The lattice parameter of as-spun ribbons is increased from 2.9905Angstrom to 2.9931Angstrom by annealing at 973K for 12h, indicating that thermal vacancies retained in the as-spun ribbons by the rapid solidification were removed out during the heat treatment. Pressure-composition isotherms were measured for both the a s-spun and annealed ribbons at temperature from 403K to 473K using an automatic Sieverts' type apparatus. The variation in hydrogen absorption capability dependent on lattice parameter change is found in the as-spun and annealed ribbons. Although both of the as-spun and annealed ribbons have almost the same lattice parameters, hydrogenation characteristics are clearly different between them.