A control system of a machine tool includes an analysis device, the analysis device includes acquisition portions which acquire chronological control data when a work is machined and which acquire spatial machined surface measurement data after the machining of the work, a storage portion which stores the control data and the machined surface measurement data, a data-associating processing portion which associates the control data and the machined surface measurement data with each other in two machining directions, a machined surface failure detection portion which detects a failure on the machined surface of the work and a location thereof based on the machined surface measurement data in the two machining directions and an identification portion which identifies a drive axis that causes the failure from the detected failure and the machining direction of the control data corresponding to the detected failure location.