This is an animal experiment immobilization device developed for radiation experiments, allowing fast and precise immobilization of the heads and torsos of mice and rats of various sizes, enabling radiation exposure experiments without anesthesia. The immobilization device features the use of magnets for easy assembly and mobility, allowing for precise setup and checks with millimeter-scale markings on the product. The body is made of acrylic, facilitating accurate scan and distortion-free radiation dose calculations through CT imaging. Partial customization of functions is possible depending on the user’s experimental environment and conditions, and color options are also available upon user request.