A plurality of smoke injection needles are inserted into or then withdrawn from tuna meat while bubbles of smoke are ejected from the smoke injection needles at intervals. The smoke is produced by burning a smoking material and containing carbon monoxide (CO) gas. The bubbles of the smoke are thus dispersed and injected into the tuna meat, and the residual CO concentration in the tuna meat is thereby set at 1100 to 2400 g/kg. The resulting smoked tuna meat M is preserved in frozen storage at about -18C.