PURPOSE: To accomplish heating of a solid food to at least its sterilizing temperature smoothly without any fear of getting out of shape at a controlled rate of temperature rise by continuous electric current heating with resistance.

CONSTITUTION: A solid food 15, together with an electrically conductive fluid 11, is passed through a electric current heating bath 1 while energizing a circuit between electrodes 3a and 3b facing to each other. Said heating bath 1 is that at least a pair of electrodes 3a, 3b facing to each other in the diameter direction for the peripheral wall section 2 with the electrode surface 8c forming a plane essentially common to the inner peripheral surface 2c of said wall section 2 are installed in plural pairs in various diameter directions. When said solid food is a raw vegetable food, it is preferable that the current be a high-frequency one with a frequency of 200KHz to 50MHz and, on exceeding ca.40°C, be replaced by electric current of commercial freqnency.