An inspection system, comprising: a data acquisition means (403, 2011a, 2011b) configured to acquire measured data being time-series data of measured values to be measured by causing a railway vehicle including a vehicle body, a bogie (12a, 12b), and a wheel set (13, 13a-13d) to travel on a track; a first track state calculation means configured to calculate an estimated value of a first physical quantity; a correction amount calculation means configured to calculate a correction amount for the estimated value of the first physical quantity based on the estimated value of the first physical quantity calculated by the first track state calculation means and an actual value of the first physical quantity; a second track state calculation means configured to calculate an estimated value of the first physical quantity after the correction amount is calculated; and a track state correction means configured to correct the estimated value of the first physical quantity calculated by the second track state calculation means by using the correction amount, wherein the measured data contain a measured value of a forward-and-backward-direction force (T 1 -T 4), the forward-and-backward-direction force (T 1 -T 4) is a force in a forward and backward direction (x) to occur in a member disposed between the wheel set (13, 13a-13d) and the bogie (12a, 12b) on which the wheel set (13, 13a-13d) is provided, the member is a member for supporting an axle box, the forward and backward direction (x) is a direction along a traveling direction of the railway vehicle, the first physical quantity is a physical quantity reflecting a state of the track, the first track state calculation means and the second track state calculation means are configured to use a relational expression representing the relation between the first physical quantity at a position of the wheel set (13, 13a-13d) and the forward-and-backward-direction force (T 1 -T 4) and a measured value of the forward-and-backward-direction force (T 1 -T 4) to calculate the estimated value of the first physical quantity, the measured value of the forward-and-backward-direction force (T 1 -T 4) used in the first track state calculation means is contained in the measured data acquired by the data acquisition means (403, 2011a, 2011b) before the correction amount is calculated, and the measured value of the forward-and-backward-direction force (T 1 -T 4) used in the second track state calculation means is contained in the measured data acquired by the data acquisition means (403, 2011a, 2011b) after the correction amount is calculated. a data acquisition means (403, 2011a, 2011b) configured to acquire measured data being time-series data of measured values to be measured by causing a railway vehicle including a vehicle body, a bogie (12a, 12b), and a wheel set (13, 13a-13d) to travel on a track; a first track state calculation means configured to calculate an estimated value of a first physical quantity; a correction amount calculation means configured to calculate a correction amount for the estimated value of the first physical quantity based on the estimated value of the first physical quantity calculated by the first track state calculation means and an actual value of the first physical quantity; a second track state calculation means configured to calculate an estimated value of the first physical quantity after the correction amount is calculated; and a track state correction means configured to correct the estimated value of the first physical quantity calculated by the second track state calculation means by using the correction amount, wherein the measured data contain a measured value of a forward-and-backward-direction force (T 1 -T 4), the forward-and-backward-direction force (T 1 -T 4) is a force in a forward and backward direction (x) to occur in a member disposed between the wheel set (13, 13a-13d) and the bogie (12a, 12b) on which the wheel set (13, 13a-13d) is provided, the member is a member for supporting an axle box, the forward and backward direction (x) is a direction along a traveling direction of the railway vehicle, the first physical quantity is a physical quantity reflecting a state of the track, the first track state calculation means and the second track state calculation means are configured to use a relational expression representing the relation between the first physical quantity at a position of the wheel set (13, 13a-13d) and the forward-and-backward-direction force (T 1 -T 4) and a measured value of the forward-and-backward-direction force (T 1 -T 4) to calculate the estimated value of the first physical quantity, the measured value of the forward-and-backward-direction force (T 1 -T 4) used in the first track state calculation means is contained in the measured data acquired by the data acquisition means (403, 2011a, 2011b) before the correction amount is calculated, and the measured value of the forward-and-backward-direction force (T 1 -T 4) used in the second track state calculation means is contained in the measured data acquired by the data acquisition means (403, 2011a, 2011b) after the correction amount is calculated.