A device (DA) analyses an immersive virtual reality system (SI) comprising a target (CD) that is securely fastened to an object (OM), detecting means (MD) that deliver a first signal representative of the current position of the target (CD), processing means (MT) that define images depending on the detected current position, and at least one image-displaying means (EA, PI). This device (DA) comprises a first sensor (C1) that generates a second signal when the object (OM) reaches a known position, a second sensor (C2) that generates a third signal when it detects a change in displayed image consecutive to the detection of the object (OM) in this known position by the detecting means (MD), and analysing means (MA) that determine first and second times of reception of the second and third signals then a first time difference between these first and second times of reception.