There is provided a series of coelenterazine (CTZ) derivatives as a substrate with high luminescence intensity, which is optimal for maximum luminescence wavelengths at both 400 nm (blue-shifted RLuc luminescence system) and 500 nm (ALuc luminescence system) for bioassays which is more sensitive than known techniques. The novel CTZ derivatives are compounds in which a specific position(s) of the CTZ is/are substituted with a specific substituent(s) as shown, for example, by the Formula [I], and has a higher luminescence intensity than known CTZ derivatives in blue-shifted RLuc luminescence system or ALuc luminescence system.