This paper investigates how macroeconomic monetary shock and microeconomic financial distress affect the determination of trade credit usage in short-term debt market of Korean economy. There is a general notion that trade credit is considerably more expensive than short-term bank financing, revolving line, as trade credit is preferred by the firms facing obstacles to obtain financing from banks. In corporate debt market, it is prevailing wisdom that the reliance on vendor financing increases with the degree of credit rationing on financially constrained firms. This paper examines whether bank loan lending channel and trade credit lending channel are substitutes or complements at the time of contracting monetary policy, financial constraints, and financial crisis. This paper provides finding that bank loan and trade credit are substitutes and both are pro-cyclical. These findings are opposite to those of industrialized countries such as US and Western European counties while they are in accordance with those of Japan, Spain, and Italy. This paper also finds that the various aspects of financial constraints of a firm increase the usage of trade credit lending channel.