An insertion state determination system includes a sensor unit including a first sensor and the system includes a second sensor and a processor. The first sensor is configured to determine a first rotation amount indicating a rotation amount of an elongated insertion unit of an endoscope device around a center axis of the insertion unit. A hole through which the insertion unit passes is formed in the sensor unit. The second sensor is disposed in the sensor unit or an object fixed to the sensor unit and is configured to determine a second rotation amount indicating a rotation amount of the sensor unit around the center axis when the insertion unit is inserted into the subject. The processor is configured to calculate a corrected rotation amount by correcting the first rotation amount based on the second rotation amount.