The global pet market is continuously growing as the number of single-person households increases along with the preponderance of the nuclear family, so pet-related industries are steadily growing. In addition, the market related to the health of companion animals is also increasing significantly. Regarding the health of companion animals, it is reported that the incidence of adult diseases, like humans, is growing mainly due to activities in indoor environments and the lack of exercise due to the lack of time for companion animals. This paper studies the antioxidant properties of Jerusalem Artichoke extract, which can be used as a raw material for functional foods related to adult diseases in companion animals by using substances extracted from Jerusalem Artichokes grown by the first author. Samples to be tested were extracted from hot water extraction and ethanol extraction methods according to conditions. To confirm the antioxidant properties, absorbance analysis, thin-layer chromatography (TLC) analysis, polyphenol measurement, flavonoid measurement, and radical scavenging ability measurement by DPPH were performed to determine whether the raw materials applied in this paper could be used. It was confirmed that Jerusalem Artichoke extract is a suitable additive raw material for functional pet food.