An in-vehicle display device includes video input section into which a picture output from mobile terminal is input and display connected to video input section via video output controller and video output section. An output section of video input section is connected to an input section of image characteristics detector, an output section of image characteristics detector is connected to a first input section of image discriminator, an output section of vehicle operating state detector is connected to a second input section of image discriminator, and an output section of the image discriminator is connected to an input section of video output controller. Further, image discriminator compares an output from image characteristics detector with an output from vehicle operating state detector, and controls an output to video output controller.