To provide a carrier where a selectively bindable substance having an excellent S/N ratio at detection is immobilized.

This immobilized carrier of the selectively bindable substance wherein the selectively bindable substance is immobilized on the carrier surface has characteristics wherein the carrier surface comprises a saturated annular polyolefin-based resin, and the carrier is provided with an irregularity part, and the selectively bindable substance is immobilized on the upper surfaces of a plurality of projection parts of the irregularity part.