An image-capturing device and a projection automatic calibration method of a projection device are provided. The image-capturing device includes an image sensing device, a lens, a processing unit and a storage unit. The lens is configured to image a calibration pattern on the image sensing device. The processing unit is configured to issue a projection calibration requirement and analyze the calibration pattern imaged on the image sensing device to obtain information relating to the calibration pattern, and the processing unit is further configured to convert imaging coordinates of the calibration pattern imaged on the image sensing device into projecting coordinates of the projection device by executing a calibration driving program to establish a coordinate conversion table. The storage unit is configured to store the calibration driving program and the coordinate conversion table.