Insect sperm flagella show wide variety of their internal structures and beating patterns. Accurate description of the features will provide important information for understanding the mechanism of axonemal structure and the corresponding bending wave generation. Here, we focus on spermatozoa of Drosophila melanogaster, which has an extremely long flagellum with a length of 2 millimeters. Its internal structure, axoneme has 9+9+2 architecture, distinct from conventional 9+2 axoneme. Unlike axonemes from the flagella of Chlamydomonas or sea urchins, the constituent proteins of axonemes of Drosophila sperm have not been well characterized. Nevertheless, Drosophila axonemes have many advantages over axonemes from other sources. (1) Drosophila is one of the best-established laboratory animals. It has a short life cycle and is easy to breed. (2) Complete genome information is available. (3) A vast number of mutants have been created, natural or transgenic, and many of them are available from stock centers worldwide. Taking these advantages, here, we isolated spermatozoa from the testes and recorded their movement with a high-speed camera. The spermatozoon swims in a spiral pathway in the radius of a few hundred micrometers, and the beating wave consists of minor waves (20-30 Hz, wavelength = ca. 30 μm) superimposed on major waves. Although its physiological significance is unclear, the double-wave nature of the beating pattern could be related to the 9 + 9 + 2 architecture. When combined with the genetic resource of Drosophila, the precise observation will provide a powerful clue for studying the structure-function relationship of eukaryotic flagella in general. This work was supported by JSPS KAKENHI, 26440089 and 17K07376 to K.O., JP16H06280, the Takeda Science Foundation (K.O.) and Hyogo Science and Technology Association (K.O.).