A control system of a machine tool includes an analysis device, the analysis device includes acquisition portions which acquire chronological speed control data when a work is machined and which acquire spatial machined surface measurement data after the machining of the work, a data-associating processing portion which associates the speed control data and the machined surface measurement data with each other, a machined surface failure detection portion which detects a failure depth of a failure location on the machined surface of the work and an identification portion which identifies the control data of the failure location corresponding to the machined surface measurement data of the failure location so as to identify a failure depth corresponding to the control data of the failure location and the numerical control device corrects the control data based on the control data of the failure location and the corresponding failure depth.