The present invention includes: a char feeding hopper body that feeds separated char toward a coal gasifier; a char communicating tube that communicates with a bottom portion of the char feeding hopper body and extends in a vertical axis direction; fluid gas feeding means that is provided at a bottom portion side of the char feeding hopper body and feeds fluid gas to an inside thereof; a radiation source section that emits γ-rays toward an inside of the char communicating tube in which a level of the char reaches a level H2 which is the same level as a level H1 of the char in the char feeding hopper as a result of feeding of the fluid gas; and a γ-ray detector that is provided along a vertical axis direction of the char communicating tube and detects the emitted γ-rays.