A hypnotic/sedative agent comprising methyl 3-[(4S)-8-bromo-1-methyl-6-(2-pyridinyl)-4H-imidazo[1,2- a][1,4]benzodiazepin-4-yl]propanoate or a salt thereof is administered to a vein of a patient by a two-step administration method as disclosed in the present invention, whereby general anesthesia can be introduced safely and rapidly and the state of general anesthesia can be maintained.