1. A method for recognizing, by a terminal device using a convolutional neural network, a card number and expiration date of a card, the method comprising steps of: (a) obtaining an image of the card through a camera; (b) performing, using the convolutional neural network, position detection and number recognition on card numbers within the image obtained at the step (a), wherein the step (b) comprises: (1) detecting a position of a first number of the card numbers, (2) detecting positions of first three card numbers of the card numbers, (3) determining whether an image patch of the first three card numbers recognized at the step (2) corresponds to numbers, (4) comparing a recognition probability value with a predetermined threshold if, as a result of the determination at the step (3), it is determined that the image patch of the first three card numbers correspond to numbers, and recognizing the first three card numbers, (5) extracting information about a card type, a card number format, positions of expiration date numbers, and a format of the expiration date numbers from the first three card numbers recognized at the step (4), and (6) performing position detection and number recognition on remaining card numbers other than the first three card numbers using the information extracted at the step (5); and (c) performing, using the convolutional neural network, position detection and number recognition on the expiration date numbers within the image obtained at the step (a), wherein the card is a credit card.