This paper combines the concepts of traditional rent-seeking theory and criminal economics to establish a model of rent seeking which takes the coexistence of legal and illegal rent seeking activities into consideration. Using this model, we analyze how judicial investigation and scale of punishment of illegal rent seeking activities will affect social rent seeking waste. Our findings show that the strengthening of government investigation or punishment of illegal rent seeking activities will increase rather than decrease social rent seeking waste, provided that the sufficient condition proposed by this paper is satisfied.