Tire condition detecting device and a tire condition detection method

Tire condition detecting apparatus capable of detecting a condition of the tire with high precision. Tire condition detection device (10) is a device that detects a tire condition of a pneumatic tire which is fixed to the wheel (108), the vibration input unit for inputting a predetermined vibration to the tire (310), predetermined vibration There frequency information acquisition section which acquires the frequency information of the tire (108) when it is entered (320), extracts a resonant frequency of the tire (108) from the acquired frequency information extracted resonance of the tire (108) the frequency, outside the moment of inertia of the tire (108), an inner moment of inertia, and when the modeled using the spring constant of elastic force acting between the tire state estimation unit for calculating a spring constant and a (330) a.