Reversible child seat with single seat belt passages

The seat has an armchair including a backrest (22) whose upper part is provided with strap passages (25) i.e. slots, where each strap passage receives a chest strap (61) of a safety belt of a motor vehicle in a position in which an infant faces the road and in another position in which back side of the infant faces the road. The chest strap circulates in the corresponding strap passage in the two positions. Indicators (62, 63) e.g. blue and red color elements, are placed at the proximity of each strap passage to indicate that the strap passage receives the chest strap in the two positions.