A front passenger seat airbag device , comprising: an airbag cushion that expands and deploys above an instrument panel of a vehicle and between the instrument panel and a front passenger seat in a condition contacting an upper surface of the instrument panel ; and an inflator that supplies gas to the airbag cushion , the inflator being secured to an inner side of the instrument panel ; wherein the airbag cushion includes: a pair of side panels that form side portions on two sides of the airbag cushion in a vehicle width direction, and a strip-shaped main panel connecting edges of the pair of side panels to each other; the pair of side panels have an acute angle portion that extends along the upper surface of the instrument panel toward the front of the vehicle at an acute angle; and the airbag cushion further includes: an inner seam margin in which an edge of the main panel and edges of the pair of side panels are joined in a condition bent to the inner side of the airbag cushion , and an outer seam margin in which end portions on two sides of the main panel in a longitudinal direction are vertically overlapped and joined in a state further extending to the front of the vehicle from the acute angle portion of the pair of side panels . an airbag cushion that expands and deploys above an instrument panel of a vehicle and between the instrument panel and a front passenger seat in a condition contacting an upper surface of the instrument panel ; and an inflator that supplies gas to the airbag cushion , the inflator being secured to an inner side of the instrument panel ; wherein the airbag cushion includes: a pair of side panels that form side portions on two sides of the airbag cushion in a vehicle width direction, and a strip-shaped main panel connecting edges of the pair of side panels to each other; the pair of side panels have an acute angle portion that extends along the upper surface of the instrument panel toward the front of the vehicle at an acute angle; and the airbag cushion further includes: an inner seam margin in which an edge of the main panel and edges of the pair of side panels are joined in a condition bent to the inner side of the airbag cushion , and an outer seam margin in which end portions on two sides of the main panel in a longitudinal direction are vertically overlapped and joined in a state further extending to the front of the vehicle from the acute angle portion of the pair of side panels . a pair of side panels that form side portions on two sides of the airbag cushion in a vehicle width direction, and a strip-shaped main panel connecting edges of the pair of side panels to each other; the pair of side panels have an acute angle portion that extends along the upper surface of the instrument panel toward the front of the vehicle at an acute angle; and the airbag cushion further includes: an inner seam margin in which an edge of the main panel and edges of the pair of side panels are joined in a condition bent to the inner side of the airbag cushion , and an outer seam margin in which end portions on two sides of the main panel in a longitudinal direction are vertically overlapped and joined in a state further extending to the front of the vehicle from the acute angle portion of the pair of side panels . an inner seam margin in which an edge of the main panel and edges of the pair of side panels are joined in a condition bent to the inner side of the airbag cushion , and an outer seam margin in which end portions on two sides of the main panel in a longitudinal direction are vertically overlapped and joined in a state further extending to the front of the vehicle from the acute angle portion of the pair of side panels . <EOS>