Provided is a thoracic cavity simulator that, for the purpose of training or education in thoracic cavity microscopic surgery, faithfully reproduces the shape and feel of a human body and that can simulate a surgical environment for a human body that has multiple constraints. A device that comprises a model human skeleton that simulates at least ribs, and comprises a casing that houses the model human skeleton, the device being configured such that an opening is provided to a rib section of the casing, such that a diaphragm section can be opened and closed, and such that model organs can be housed inside the ribs of the model human skeleton. The diaphragm section is configured so as to be removable and/or openable and closable, and the model organs housed inside the ribs of the model human skeleton are replaced.