A two-pack urethane-based adhesive that includes a second-pack liquid in which liquid components are inhibited from bleeding out and which can be inhibited from decreasing in thixotropic properties, and that gives cured products having, after aging, excellent adhesiveness. The two-pack urethane-based adhesive including a first-pack liquid, which includes a urethane prepolymer having an isocyanate group, and a second-pack liquid, which includes water, an active hydrogen compound (which is not water) having an active hydrogen capable of reacting with the isocyanate group, and cellulose nanofibers, wherein the first-pack liquid and the second-pack liquid each independently contain carbon black and/or an inorganic-based filler, the content of the cellulose nanofibers being 0.1-1.5 mass % with respect to the content of the water.