The present invention suggests a method for providing a QR code-based service for checking whether or not a cocktail effect of drugs will occur using a smart device, which enables even an ordinary person with no specialist expertise to easily check whether or not a cocktail effect will occur when taking a plurality of drugs and to refrain from administration of a drug which may result in a negative effect, and thus, can prevent the abuse of drugs, by extracting drug information by scanning a QR code provided on the package of the drug to be taken, which a user intends to take, by means of a smart device, determining, using administration information previously registered in a database, whether or not the drug being taken and the drug to be taken cause a cocktail effect due to an interaction caused thereby, and outputting the determination result.