An adhesive composition for forming an adhesive layer that can bond a first substrate formed of a semiconductor-forming substrate to a second substrate formed of a support substrate in a peelable manner, the composition containing a component (A) which is cured through hydrosilylation and a peeling component (B) which contains a component containing an epoxy-modified polyorganosiloxane, wherein the component (A) contains a polysiloxane (A1) including a siloxane unit represented by SiO2 (unit Q) and the like, and a platinum group metal catalyst (A2); and the polysiloxane (A1) contains a polyorganosiloxane (a1) including a siloxane unit represented by SiO2 (unit Q′) and the like, and a polyorganosiloxane (a2) including a siloxane unit represented by SiO2 (unit Q″) and the like, and having a functional group (Si—H) content of 5.0 mol/kg or greater.