Provided are a sensing device and a biosensor that are capable of achieving stable performance in sensing saccharides or hydroxyl group-containing polymers, and that can be stored for a long time. The biosensor 8 of the present invention uses, as a component for sensing glucose, a sensing device 16 in which a completely synthetic phenylboronic acid compound 21 is bound without using enzymes that have been conventionally used. Consequently, the biosensor 8 can eliminate the problem of protein denaturation to achieve stable performance in sensing glucose, and it is possible to achieve the biosensor 8 can be stored for a long time.