Azodicarbonamide (ADA) is used in some countries as a flour bleaching agent and a dough conditioner. However, ADA is prohibited for use as a food additive in Japan. Therefore, it is necessary to establish an efficient and sensitive method to determine ADA in wheat flour. A simple and practical procedure to analyze ADA in wheat flour and prepared flour mixes was developed. ADA was extracted from samples by ultrasonication with acetone. ADA in the solution was derivatized with triphenylphosphine (TPP). The ADA-TPP derivative was concentrated and cleaned up using a reversed-phase solid-phase extraction cartridge, and the ADA-TPP derivative was analyzed using HPLC for determination and LC-MS/MS for identification. Good linearity was achieved over the concentration range of 0.25-100 ppm ADA in wheat flour and prepared flour mixes. The mean recoveries from wheat flour and prepared flour mixes fortified at the levels of 1 and 10 ppm ranged from 86.9 to 101.0%, and the coefficients of variation ranged from 1.9 to 3.4%.