An image processing apparatus processes an image by using one or more neural networks, and includes a memory storing one or more instructions and data structures for a main neural network and a sub-neural network, and a processor configured to execute the one or more instructions stored in the memory to process an input image by using the main neural network to obtain intermediate result data and a final output image, and to process the intermediate result data by using the sub-neural network to output an intermediate image while the input image is being processed by using the main neural network.