Abstract: The present invention provides methods whereby an RNAi activity and a miRNA activity can be evaluated simply and conveniently. The RNAi activity or the miRNA activity is evaluated by supplying a target-expressing molecule, which is a polynucleotide containing at least a target sequence and an expression regulatory region regulating the expression of an RNA containing the target sequence, and a subject nucleic acid molecule to be evaluated on whether or not it has RNAi activity on the RNA containing the target sequence into an expression system in which the target-expressing molecule can express the RNA containing the target sequence.