A floating type air bag device able to prevent backlash of a module cover and easily position the module cover with respect to a steering wheel without dispersion and a sacrifice of an operation feeling of horn sounding is provided. The air bag device has a retainer (10) to which an inflator and a folded air bag are attached, the retainer (10) being fixed to a steering wheel armature (60) and having a plurality of hooks (13) formed in a side wall portion thereof (12); a module cover (20) in which the module cover covers the air bag and the hook (13) is engaged with an opening (22b) of a leg piece portion (22) projected from a rear side and the module cover (20) can be vertically moved with respect to the retainer (10); a horn plate (30) attached along a circumferential edge of the module cover (20); a contact plate (40) attached to an extending-out portion (11) of the retainer (10) or the horn plate (30); and a horn spring (50) arranged between the horn plate (30) and the retainer (10); wherein a first position regulation section (pin) (11d) of the retainer (10) to the steering wheel (60) is received by a resin coating portion (62) of the steering wheel armature, and is placed below a second position regulation section (C) formed by the opening (21a) of the leg piece portion (21) of the module cover (20) and a pawl (11c) extended in the retainer (10).