The present invention provides a tire internal pressure warning system, comprising: an internal pressure data acquisition apparatus for obtaining data of internal pressure of each tire 5 of a vehicle 6 (a TPMS sensor transmitter 1 and a TPMS receiver 2); and an information terminal device 3 for determining whether there is a puncture-based failure or a failure resulting from a natural pressure drop, based on a change in the internal pressure of each tire received from the TPMS receiver 2, and displaying a warning in accordance with the failure condition.