A ridge waveguide (10) according to the present invention includes a ridge part (11), the ridge part (11) being in contact with both a side (14) in a long-side direction and a side (15) in a short-side direction in a cross-sectional shape of the ridge waveguide. Further, an array antenna apparatus according to the present invention includes a feeder circuit formed by a ridge waveguide (10) including a ridge part (11), the ridge part (11) being in contact with both a side (14) in a long-side direction and a side (15) in a short-side direction in a cross-sectional shape of the ridge waveguide. In this way, it is possible to provide a ridge waveguide that can be easily manufactured.