To provide a data management system or the like by which a distance between a data measuring instrument 14 or the like, e.g., a body composition monitor and a PC 11 is not restricted to a wire cable, a troublesome operation, e.g., attachment/detachment of a memory medium for data exchange is not required, input of measurement data, e.g., a health testing data does not take trouble, and a device structure is inexpensive. When a communication button 21 is pushed, a relay key 12 transmits predetermined information to a data measuring instrument 14 or the like. The data measuring instrument 14 or the like transmit measurement data to the relay key 12 side. The relay key 12 transmits to the PC 11 measurement information based on the received measurement data. The PC 11 transmits to a provider side server 44 the measurement information transmitted from the relay key 12. The provider side server 44 records the transmitted measurement information in a database DB 46 based on a predetermined format, and allows the PC 11 side to browse the measurement information recorded in the database DB 46.