In a sensor data acquisition terminal (10), an NTP back-end processing unit (12) synchronizes a terminal timing with a parent terminal timing by exchanging NTP packets for time synchronization with a parent terminal (20) based on NTP, and a protocol conversion unit (13) converts an NTP packet, which is output from the NTP back-end processing unit (12) and will be transmitted to the parent terminal (20), to a TPSN packet based on TPSN, outputs the TPSN packet to a wireless processing unit (14), converts a TPSN packet from the parent terminal (20), which is output from the wireless processing unit (14), to an NTP packet, and outputs the NTP packet to the NTP back-end processing unit (12).