A device for starting an occupant crash protector can output, as a start signal, a logical product of an output of a collision determining mechanism and an output of a non-collision determining mechanism. The collision determining mechanism detects a collision including an impact that does not require a start-up. The non-collision determining mechanism detects only a collision that requires a start-up using a value obtained by subtracting a value varied with time from the output of an acceleration sensor and integrating the result of the subtraction.
