A dyeable polyolefin fiber includes a sea-island structure in which a polyolefin (A) is the sea component and a copolyester (B) obtained by copolymerizing cyclohexanedicarboxylic acid is the island component, the polyolefin fiber characterized in that the dispersion diameter of the island component in a lateral cross section of the fiber is 30 to 1000 nm. The dyeable polyolefin fiber is bright, deep coloring is imparted to the lightweight polyolefin fiber, oxidative decomposition during tumbler drying and yellowing during long-term storage are minimized, and the polyolefin fiber can be suitably used as a fibrous structure.