An ink composition is provided that includes (Component A) at least one compound selected from the group consisting of bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide and 2,4,6-trimethylbenzoyldiphenylphosphine oxide, (Component B) at least one compound selected from the group consisting of 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one, 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholinyl)phenyl]-1-butanone, and 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone, (Component C) a thioxanthone compound, (Component D) a polymerization inhibitor, and (Component E) a polymerizable compound, Component C having a content of 0.01 to 5 wt % relative to the total weight of the ink composition, Component D having a content of 0.01 to 5 wt % relative to the total weight of the ink composition, the sum of the content of Component A and the content of Component B being 6.0 to 9.5 wt % relative to the total weight of the ink composition, and the ratio by weight ((A)/(B)) of the content (A) of Component A and the content (B) of Component B being 0.8 to 2.0.