To obtain the subject composition capable of exhibiting excellent curability by compounding a compound containing oxetane ring and a photo- cationic polymerization initiator consisting of a sulfonium salt having a maximum molar extinction coefficient higher than a specific level at a wavelength within a specific range.

This composition contains (A) a compound having oxetane ring, (B) a photo-cationic polymerization initiator consisting of a sulfonium salt having a maximum molar extinction coefficient of ≥100 in a wavelength range of 360nm to 500nm and (C) a pigment as an arbitrary component. Especially preferable example of the component B is a sulfonium salt having thioxanthone structure. The ratios of the components A and B in the composition are preferably 20-99.9wt.% and 0.1-20wt.%, respectively. The amount of the component C is preferably 0-200 pts.wt. based on 100 pts.wt. of the sum of the other components. Especially, a pigment-colored cured product having excellent curability, gloss, etc., and exhibiting excellent physical properties can be produced from the composition.