To provide a temporary fixing method for the processing of an optical part and a composition suitable for the method.

The composition contains (A) a polyfunctional (meth)acrylate, (B) a monofunctional (meth)acrylate, (C) a photopolymerization initiator, (D) a polar organic solvent and (E) a particulate substance insoluble in the components (A) to (D). Preferably, the component (E) has spherical form and is more preferably one or more materials selected from crosslinked polymethyl methacrylate particles, crosslinked polystyrene particles and spherical silica particles, and the component (D) is one or more materials selected from methanol, ethanol, isopropyl alcohol and n-butanol. The temporary fixing method for a part comprises the bonding and temporary fixing of the part with the composition, the processing of the temporarily fixed part and the immersion of the processed part in hot water of ≤90°C to remove the cured material of the composition.