The present invention relates to a compound represented by the following formula [I]wherein each symbol is as defined in the specification, or a pharmaceutically acceptable salt thereof, or a solvate thereof and an anti-HCV agent and an HCV polymerase inhibitor containing this compound. The compound of the present invention shows an anti-HCV activity based on the HCV polymerase inhibitory activity, and useful as an agent for the prophylaxis or treatment of hepatitis C.