A simulator for estimating a behavior of a system (1, 2) to be simulated, the system (1, 2) including a processing device (210, 311, 313) for processing a target, a carrier (230, 240) configured to transport the target, and a visual sensor, the simulator comprising: a creating unit configured to create a virtual system of the system (1, 2) to be simulated in a three-dimensional virtual space, wherein the virtual system includes a virtual processing device, a virtual target, and a virtual carrier configured to transport the virtual target; a visual sensor simulator configured to perform image measurement of an input image including at least a part of the virtual target as a subject of the image in a manner associated with a first area predefined at a predetermined position in the three-dimensional virtual space, wherein the predetermined position is on a transporting path of the virtual carrier, wherein the image measurement includes searching the input image for a part corresponding to one or more pieces of predetermined reference information by calculating a degree of correspondence between the one or more pieces of predetermined reference information and the input image, and wherein the visual sensor simulator outputs, as a measurement result, a rotation angle of a part corresponding to at least one of the pieces of reference information included in the input image; and a controller simulator configured to generate a control instruction directed to the virtual processing device based on the measurement result obtained by the visual sensor simulator; characterized by a reproduction unit configured to reproduce, in the virtual system, a behavior of the virtual target detected in the input image together with information about a type and an orientation of the detected virtual target based on time-series data outputted from the controller simulator and the measurement result obtained by the visual sensor simulator, wherein the reproduction unit uses the time-series data to reproduce chronological changes of the virtual target and the virtual processing device in the virtual system, and wherein the reproduction unit generates information about the orientation of the virtual target based on the rotation angle output as the measurement result. a creating unit configured to create a virtual system of the system (1, 2) to be simulated in a three-dimensional virtual space, wherein the virtual system includes a virtual processing device, a virtual target, and a virtual carrier configured to transport the virtual target; a visual sensor simulator configured to perform image measurement of an input image including at least a part of the virtual target as a subject of the image in a manner associated with a first area predefined at a predetermined position in the three-dimensional virtual space, wherein the predetermined position is on a transporting path of the virtual carrier, wherein the image measurement includes searching the input image for a part corresponding to one or more pieces of predetermined reference information by calculating a degree of correspondence between the one or more pieces of predetermined reference information and the input image, and wherein the visual sensor simulator outputs, as a measurement result, a rotation angle of a part corresponding to at least one of the pieces of reference information included in the input image; and a controller simulator configured to generate a control instruction directed to the virtual processing device based on the measurement result obtained by the visual sensor simulator; characterized by a reproduction unit configured to reproduce, in the virtual system, a behavior of the virtual target detected in the input image together with information about a type and an orientation of the detected virtual target based on time-series data outputted from the controller simulator and the measurement result obtained by the visual sensor simulator, wherein the reproduction unit uses the time-series data to reproduce chronological changes of the virtual target and the virtual processing device in the virtual system, and wherein the reproduction unit generates information about the orientation of the virtual target based on the rotation angle output as the measurement result.