A prepackaged food sterilizing apparatus for sterilizing a prepackaged food P has a high frequency generator 71. A high frequency is supplied from the high frequency generator 71 to the prepackaged food P to sterilize the prepackaged food P by dielectric heating. The apparatus includes a food loading container 2x constituted by a pair of opposing electrodes 20 consisting of a lower electrode 210 and an upper electrode 220 to which the high frequency is supplied and an annular insulator 23 interposed between the opposing electrode pair 20. The food loading container 2x has at least one food loading chamber 21 in which the prepackaged food P is loaded with an inner shape thereof substantially equal to an outer shape of the prepackaged food P.