Disclosed is an adamantane derivative which provides a cured product excellent in optical characteristics such as transparency and light resistance, long-term heat resistance, electrical characteristics such as and dielectric constant, and low water absorption. Also disclosed are a resin composition containing the adamantane derivative, a sealing agent for electronic circuits, optical electronic member, semiconductor device and copper-clad laminate all using the resin composition, and a radiation-sensitive resin composition which contains the above-mentioned adamantane derivative as a crosslinking agent. Specifically disclosed are an adamantane derivative represented by the formula (I-1) below, a resin composition containing the adamantane derivative, a sealing agent for electronic circuits, optical electronic member, semiconductor device and copper-clad laminate, all using the resin composition, and a radiation-sensitive resin composition which contains the above-mentioned adamantane derivative as a crosslinking agent.