To provide a device for preventing an accident of stepping off the stairs, which happens when going down the stairs holding things in hands and being unable to look ahead, especially in the most dangerous case when it is hard to judge whether there is another step or not before the last step.

Switches are provided in treads of the bottom stair of the staircase and another two steps above it. When descending the stairs, the weight is applied in order from the upper stair, the middle stair to the lowest stair while the switch on each stair is closed by the weight and a circuit for a buzzer, a speaker and a lamp, which is composed serially in each stair, is open after a certain period of time. The buzzer sounds differently on each tread of the stairs, so that the position on the upper, the middle or the lowermost step can be located. At the same time, a panel light having a different luminescent color depending on the stair case location is lighted up, and thus the person descending the stairs listens to the buzzer and looks at the panel light so as to judge on which tread from the last one of the stairs he/she is stepping on then.