Measurement of sonoluminescence is an effective method to evaluate a reaction field induced by intense ultrasound in a liquid. The present paper discusses changes of intensity of sonochemical luminescence from a luminol solution under various stirring conditions. A glass beaker filled with a luminol solution was irradiated by ultrasound using Langevin‐type transducers attached to the bottom and side walls of a cooling bath. As in conventional chemical reactions, the intensity of luminescence was expected to increase with stirring operation. At 28 and 100 kHz, the luminescence intensity increased at a higher applied power and at a faster stirring speed. But, at 45 kHz where intense cavitation was observed in the present apparatus, the luminescence intensity decreased as the applied power increased while stirring with a flat paddle. This anomalous behavior was more pronounced at more intense stirring operation with an impeller. The authors reported the existence of upper threshold of sound pressure for sonoluminescence [Hatanaka etal., Jpn. J. Appl. Phys. 38, 3053–3057 (1999)]. The present results suggest that stirring operation affects the generation and growth of cavitation bubbles making them exceed the upper threshold in some cases, and that there is an optimum stirring motion for sonochemical reactions.