The relationship between the hardness of mashed potato and its swallowing characteristics were studied. The textural properties of mashed potato consisting of water or skim milk, oil and standard potato were investigated by texture measurements. In the mashed potato without oil, the addition of water or skim milk had little effect on the hardness. In the mashed potato with oil, the effect of the component ratio of water-oil-potato on the hardness was different from that of the skim milk-oil-potato. The hardness of the water-oil-potato mash was lower than that of the skim milk-oil-potato mash. We presume that this difference in the hardness of the mashed potato was due to the emulsification of the skim milk-oil-potato mash. The properties of oil and liquid (water or skim milk) for mashed potato were varied. The mashed potato with a high oil ratio was harder than that with a low oil ratio. The state of emulsification of the oil in the mashed potato sample was observed by microphotography. The sensory evaluation panel judged the mashed potato sample containing a relatively large quantity of skim milk to be the easiest to swallow.