[Problem] The present invention provides a condensed pyrrolopyridine derivative which is useful as an active ingredient for a pharmaceutical composition, in particular, a pharmaceutical composition for preventing or treating diseases caused by undesirable cytokine signal transduction or diseases caused by abnormal cytokine signal transduction. [Means for Solution] The present inventors have extensively studied a compound having a JAK inhibitory action, and as a result, they have found that a condensed pyrrolopyridine derivative which is the compound of the present invention has an excellent JAK inhibitory action, and is therefore useful as an agent for preventing or treating diseases caused by undesirable cytokine signal transduction or diseases caused by abnormal cytokine signal transduction, thereby completing the present invention.
