To provide an ink composition that is excellent in curability, blocking resistance and molding properties and hardly suffers from color changes before and after molding processing.

The ink composition comprises a polymerizable monomer, a radical polymerization initiator and a sensitizer represented by formula (C-1), where at least 65 wt.% of the polymerizable monomer is a monomer selected from the group consisting of monofunctional (meth)acrylates, monofunctional vinyl oxy compounds, monofunctional N-vinyl compounds and monofunctional (meth)acrylamides. In the formula, X is O, S or NR; R is a hydrogen atom, an alkyl group or an acyl group; n is 0 or 1; R1 to R8 are each a hydrogen atom or a monovalent substituting group; adjacent two among R1-R4 may be linked together to form a ring; and R5 or R6 and R7 or R8 may be linked to form a ring.