To avoid an air-fuel ratio from being erroneously controlled after the completion of separation of HC from an HC absorbing catalyst in an air-fuel ratio control device correcting an air-fuel ratio learning according to the air-fuel ratio of the exhaust emission on the downstream side of the HC absorbing catalyst.

When a water temperature at the time of starting is low (S31), and the HC absorbing catalyst is in the condition for starting the absorbing and collection of HC and the separation of HC is not completed within a specified time after the starting (S32), the ratio of change in air-fuel ratio on the downstream side of the catalyst relative to a change in intake air amount is calculated (S33). When the ratio is larger than a determination value (S34) set to a larger value as the water temperature is lower, a variation exceeding a variation in air-fuel ration during transient operation occurs in the air-fuel ratio. This is considered to be caused by the separation of HC, and the updating of the corrected learned value of the air-fuel ratio is prohibited (S35→S36).