Provided is a component mounting system and a mounting state inspection method in the component mounting system in which accurate mounting state inspection can be achieved with good operability. A board image capturing operation for image-capturing an inspection range of a board to be inspected to acquire captured image data is executed on the board before and after mounting work is executed on the board by inspection modules M3A and M6A. A difference between pre-mounting image data and post-mounting image data thus acquired is calculated so that each component is extracted by a component extraction processing portion 3a. The shape and position of the extracted component are compared with inspection data indicating the shape and position of a normal component stored in advance so that whether the mounting state of each component on the board is good or not, is determined by a discrimination processing portion 3b. Consequently, unstable elements in a system for recognizing and extracting each component based on color information of the component and the board can be eliminated to achieve accurate mounting state inspection with good operability.