An algorithm for odor source searching is devised by immitating the behavior of male silkworm moths. They orient towards female moths by tracking their pheromone with a characteristic behavior in which they go forward, then turn zigzag, and finally loop. In the algorithm, the time for each turn of the zigzag was made gradually longer, and the loops were adjusted so that the probability of recovering into the plume when deviated increases. The efficacy of this algorithm was validated by using a robot with gas sensors. The robot employing the algorithm was proved to be able to attain the gas source with high reliability, and also to be able to recover into the plume after straying away.