Provided is a payment method using a one-time payment security code based on a color pixel code. In the payment method, arbitrary color pixel codes are first disposed on a color grid image screen that is formed with color pixels of various colors in a smartphone-dedicated application, a user inputs a user pattern to select color pixels, a one-time payment security code is generated by combining the color pixel codes and the user pattern, and the one-time payment security code is utilized as information for paying for the user's purchase of a product or a service.