Provided is a tire pressure detection system that can be operated stably for a long period of time by using, as a power source, a secondary battery having little characteristic deterioration under a high temperature environment, e.g. in a situation in which the battery is maintained for a long period of time in a fully charged state under a high temperature environment, while having excellent low temperature characteristics. A tire pressure detection system 1 includes: an air pressure detection device 10 that detects an air pressure inside a tire; and a secondary battery 20 that supplies power to the air pressure detection device 10. The secondary battery 20 is a lithium secondary battery that includes a negative electrode containing a lithium alloy as an active material and a positive electrode.