Disclosed is a polythiocarbonate polythiol including repeating units represented by the chemical formula (I): in which formula (I), R represents a divalent hydrocarbon group, which hydrocarbon group may have at least one substituent which does not take part in a reaction with the polyisocyante component and the carbon chain in the hydrocarbon group may include at least one member selected from hetero atoms and an —OCO— group, and the polythiocarbonate polythiol has a number average molecular weight of 200 to 2500.