A two-part curable urethane composition comprising a main agent (A) and a curing agent (B), wherein the main agent (A) contains a urethane prepolymer (a), an isocyanurate-modified polyisocyanate compound (b), and a silane coupling agent (c) at a specified ratio by mass; and the curing agent (B) contains a polyether polyol (d), a polyether polyol having 4 or more hydroxy groups (e), and an amine catalyst (f) at a specified ratio by mass.