An adhesive for separatably attaching a support to a circuit side of a wafer to process a rear surface of the wafer, the adhesive including a component (A) that is cured by a hydrosilylation reaction and a component (B) containing a phenyl group-containing polyorganosiloxane, wherein a ratio in % by mass of the component (A) to the component (B) is 95:5 to 30:70. A separation method including applying the adhesive onto a first body to form an adhesion layer, attaching a second body to the adhesion layer, heating the adhesion layer from a side of the first body to cure the adhesive to form a layered body, processing the layered body, and carrying out separation between the adhesion layer, and the first and second bodies. The processing may be polishing the rear surface of the wafer.