The present invention provides a pentadienamide derivative represented by the formula (I): (wherein R1 represents substituted or unsubstituted aryl or a substituted or unsubstituted aromatic heterocyclic group; R2 represents substituted or unsubstituted aryl, a substituted or unsubstituted aromatic heterocyclic group, a substituted or unsubstituted heteroalicyclic group, or the like; R3 represents a hydrogen atom or is combined together with R4 and the adjacent nitrogen atom thereto to form a substituted or unsubstituted heterocyclic group; R4 represents substituted or unsubstituted aryl, a substituted or unsubstituted aromatic heterocyclic group, a substituted or unsubstituted heteroalicyclic group, or the like, or is combined together with R3 and the adjacent nitrogen atom thereto to form a substituted or unsubstituted heterocyclic group; and R5, R6, and R7 may be the same or different, and each represents a hydrogen atom or methyl) or a pharmaceutically acceptable salt thereof, and the like.