This paper presents mobile robot localization using coded infrared light as artificial landmark. Different from RFID, coded infrared light has highly deterministic characteristics. It is implemented with IR LEDs and phototransistors. By putting several IR LEDs on the ceiling, the floor is divided into several sectors and each sector is set to have a unique identification. Coded infrared light tells which sector the robot is in, but the size of the uncertainty is still too large if the sector size is large, which usually occurs. Dead-reckoning provides the estimated robot configuration, but the error becomes accumulated as the robot travels. This paper presents an algorithm that combines both the encoder and the coded infrared light information so that the size of the uncertainty becomes smaller. It also introduces a framework that can be used with other types of artificial landmarks. The characteristics of the developed coded infrared light and the proposed algorithm are verified from experiments.