An air-conditioning control system comprising: a terminal held by a user; an air-conditioning indoor unit; first ultrasonic sensors (M1-M4); a second ultrasonic sensor (M5-M8); an air-conditioning control device that is configured to control the air-conditioning indoor unit in accordance with a terminal position of the terminal, the air-conditioning control device comprising: an ultrasonic detection processing unit which is configured to detect ultrasonic waves emitted from the terminal through the first ultrasonic sensors (M1-M4) and the second ultrasonic sensor (M5-M8); an arrival time difference calculation unit which is configured to calculate an arrival time difference which is a difference between a time when the ultrasonic wave is detected by the first ultrasonic sensors (M1-M4) and a time when the ultrasonic wave is detected by the second ultrasonic sensor (M5-M8); a position estimation unit which is configured to estimate the terminal position of the terminal on the basis of the arrival time differences and the positions of the first ultrasonic sensors (M1-M4) and the second ultrasonic sensor (M5-M8), wherein the positions of the first ultrasonic sensors (M1-M4) are stored in the air-conditioning control device in advance and the position of the second ultrasonic sensor (M5-M8) is stored in the air conditioning-control device in advance; and an indoor unit control unit which is configured to control the air-conditioning indoor unit on the basis of the terminal position; wherein the first ultrasonic sensors (M1-M4) are provided in the air-conditioning indoor unit and the second ultrasonic sensor (M5-M8) is provided at a position different from the position of the air-conditioning indoor unit, wherein the position estimation unit is configured to estimate the terminal position of the terminal on the basis of the arrival time differences of the first ultrasonic sensors (M1-M4) using the second ultrasonic sensor (M5-M8) as a reference. a terminal held by a user; an air-conditioning indoor unit; first ultrasonic sensors (M1-M4); a second ultrasonic sensor (M5-M8); an air-conditioning control device that is configured to control the air-conditioning indoor unit in accordance with a terminal position of the terminal, the air-conditioning control device comprising: an ultrasonic detection processing unit which is configured to detect ultrasonic waves emitted from the terminal through the first ultrasonic sensors (M1-M4) and the second ultrasonic sensor (M5-M8); an arrival time difference calculation unit which is configured to calculate an arrival time difference which is a difference between a time when the ultrasonic wave is detected by the first ultrasonic sensors (M1-M4) and a time when the ultrasonic wave is detected by the second ultrasonic sensor (M5-M8); a position estimation unit which is configured to estimate the terminal position of the terminal on the basis of the arrival time differences and the positions of the first ultrasonic sensors (M1-M4) and the second ultrasonic sensor (M5-M8), wherein the positions of the first ultrasonic sensors (M1-M4) are stored in the air-conditioning control device in advance and the position of the second ultrasonic sensor (M5-M8) is stored in the air conditioning-control device in advance; and an indoor unit control unit which is configured to control the air-conditioning indoor unit on the basis of the terminal position; wherein the first ultrasonic sensors (M1-M4) are provided in the air-conditioning indoor unit and the second ultrasonic sensor (M5-M8) is provided at a position different from the position of the air-conditioning indoor unit, wherein the position estimation unit is configured to estimate the terminal position of the terminal on the basis of the arrival time differences of the first ultrasonic sensors (M1-M4) using the second ultrasonic sensor (M5-M8) as a reference. an ultrasonic detection processing unit which is configured to detect ultrasonic waves emitted from the terminal through the first ultrasonic sensors (M1-M4) and the second ultrasonic sensor (M5-M8); an arrival time difference calculation unit which is configured to calculate an arrival time difference which is a difference between a time when the ultrasonic wave is detected by the first ultrasonic sensors (M1-M4) and a time when the ultrasonic wave is detected by the second ultrasonic sensor (M5-M8); a position estimation unit which is configured to estimate the terminal position of the terminal on the basis of the arrival time differences and the positions of the first ultrasonic sensors (M1-M4) and the second ultrasonic sensor (M5-M8), wherein the positions of the first ultrasonic sensors (M1-M4) are stored in the air-conditioning control device in advance and the position of the second ultrasonic sensor (M5-M8) is stored in the air conditioning-control device in advance; and an indoor unit control unit which is configured to control the air-conditioning indoor unit on the basis of the terminal position; wherein the first ultrasonic sensors (M1-M4) are provided in the air-conditioning indoor unit and the second ultrasonic sensor (M5-M8) is provided at a position different from the position of the air-conditioning indoor unit, wherein the position estimation unit is configured to estimate the terminal position of the terminal on the basis of the arrival time differences of the first ultrasonic sensors (M1-M4) using the second ultrasonic sensor (M5-M8) as a reference.