To reduce the inspection costs for a gas pipe by carrying out inspection and measures in cooperation.

The life of a countermeasure method to be performed to a gas pipe that is buried into the ground is obtained in advance (S1). The state of the gas pipe is inspected in the execution of the countermeasure method, and inspection data are collected based on the inspection (S2). A box for inspection leading to the gas pipe is provided when the execution of the countermeasures is completed (S3). Maintenance management data are created based on the inspection data (S4). After the execution of the countermeasures, the state of the gas pipe is inspected via the box for inspection, and the inspection data based on the inspection are collected (S5). After that, the maintenance management data are updated (S6).