To provide a diagnostic system for trees, which can reduce the cost of management and care for trees in a garden and around a building and making gardening companies, reluctant to call so far, familiar to users of the system.

The system installs a camera 3 for photographing outward appearance of a tree to obtain a signal and a sensor 2 for catching a physical change in the tree or its peripheral environment to obtain a signal to the tree T, a diagnostic object, a communication device 1 at the side of the diagnostic object transfers data converted from the obtained signals to a diagnostic center via a communication network C, and the diagnostic center reproduces and records the transferred data for visual recognition and analysis by a diagnostic person.