The present invention relates toA lock hopper (11) provided with air-tight hoppers (A3, B3) arranged side by side with entrance valves (A1, B1) arranged above the air-tight hoppers (A3, B3) and exit valves (A4, B4) arranged below the air-tight hoppers (A3, B3).The lock hopper (11) performs control which alternately repeats the following states: a state in which granular substances in an upper system are placed in one of the hoppers and gas is supplied into the other hopper to discharge granular substances from the inside of the other hopper to a lower system and a state in which the granular substances in the upper system are placed in the other hopper and gas is supplied to said hopper to discharge granular substances from the inside of said hopper to the lower system.Also provided is a method of transferring granular substances in an upper system to a lower system by using above-described lock hopper, wherein gas having a volume corresponding to the volume of at least the granular substances to be discharged to the lower system is supplied to a hopper in a state in which the granular substances are being discharged from the hopper to the lower system.