To provide a block resin that has high hardness, prevents the curling of a substrate during curing and exhibits excellent mechanical characteristics such as adhesion to a substrate or the like when the block resin is used as a photocurable composition.

The block resin has a structure represented by (A)-(B)-(C) wherein each of a block (A) and a block (C) is independently a block having an ethylenically unsaturated group and a carboxyl group and a block (B) is a block free of an ethylenically unsaturated group, a carboxyl group and a hydroxyl group.