To provide a reducing agent adding device, for suitably maintaining reduction processing by adding reducing agent even when clogging occurs.

The reducing agent of an amount depending on a target adding amount Fa which is set based on an operational status of an internal combustion engine is added from an adding valve disposed upstream in exhaust to the exhaust catalyst. It is determined whether the exhaust catalyst is clogged or not, and increase correction of the target adding amount Fa is performed (S110) if the clogging is determined (YES in S108).