The invention provides a slot array antenna and a radar device. The slot array antenna achieves good radiation characteristics with a relatively simple construction. The slot array antenna includes: stacked first and second conductive members; a ridge-shaped waveguide member on the second conductive member; and conductive rods surrounding the ridge-shaped waveguide member. The waveguide member hasa waveguide face which is opposed to a conductive surface of the first conductive member and which extends along a first direction. The conductive rods each have a distal end portion facing the conductive surface of the first conductive member. The first conductive member includes first and second slot groups each arranged along the first direction. The second conductive member has a throughholewhich splits the waveguide member into first and second ridges. Some slots in the first and second slot groups are connected to a waveguide within the throughhole via a waveguide extending between thewaveguide face of the first ridge and the conductive surface, and the remaining slots are connected to the waveguide within the throughhole via a waveguide extending between the waveguide face of thesecond ridge and the conductive surface.