This paper proposes a method for speed-up of indoor self-localization system. Infrared LEDs are used as landmarks. They are invisible and thus do not irritate a human. They are set at known positions, and a CCD camera on a mobile robot observes them and self-localization is carried out. A method to obtain position in two-dimensional plane and orientation with three or more LEDs is formulated. The nonlinear least squares method is applied. Experiments verify stable self-localization when the robot moves at a speed of 50 centimeters per second.