To provide a data updating system for a microwave detector with a position detection function capable of updating a data without loading an excessive burden to a user not requiring a data updating function.

This data updating system is provided with the microwave detector 10, a download adaptor 20 connected detachably to the microwave detector, a user side cellular phone 30 connected to the download adaptor, a server side cellular phone 31 communicated with the user side cellular phone, and a server 40. The microwave detector has a microwave detection notifying function for detecting a prescribed microwave to issue an alarm, and a target notifying function for storing a position of a prescribed target and for controlling the alarm when the position of the target and the present position are under a prescribed physical relationship. New information about the position of the target is registered in the server, the user acquires downloadingly the up-to-date information from the server by the download adaptor, and registers it in the microwave detector to be updated.