A heat treatment device comprising: coagulation/dissection means having a treatment portion adapted to treat a living organism and heating means adapted to generate a heat to be applied to the organism provided in the treatment portion; applied current detection means adapted to detect a current value applied to the heating means; applied voltage detection means adapted to detect a voltage value applied to the heating means; operation means adapted to selectively perform operation of one of a current, a voltage, a power, and a temperature at the heating means using respective detection results of the applied current detection means and the applied voltage detection means; output setting means (59, 61, 62, 63, 65, 66, 67, 69, 70, 71, 73, 74) adapted for selectively setting, as a control content of an output sequence for the heating means, one of a constant current control, a constant voltage control, a constant power control, and a constant temperature control for each of two or more terms of the control content; an output sequence specifying section (84, 85, 86, 87) adapted to specify the output sequence; a transition condition setting section (78, 79, 80, 81, 82, 83) adapted to set a temperature or a time period as a transition condition between the two or more terms; output control means adapted to control an output to the heating means based on the output sequence specified by the output sequence specifying section, an operation result by the operation means, and the temperature or the time period set by the transition condition setting section; and control selection means adapted to select one of the constant current control, the constant voltage control, the constant power control, and the constant temperature control as the control of the output control means according to the control content. coagulation/dissection means having a treatment portion adapted to treat a living organism and heating means adapted to generate a heat to be applied to the organism provided in the treatment portion; applied current detection means adapted to detect a current value applied to the heating means; applied voltage detection means adapted to detect a voltage value applied to the heating means; operation means adapted to selectively perform operation of one of a current, a voltage, a power, and a temperature at the heating means using respective detection results of the applied current detection means and the applied voltage detection means; output setting means (59, 61, 62, 63, 65, 66, 67, 69, 70, 71, 73, 74) adapted for selectively setting, as a control content of an output sequence for the heating means, one of a constant current control, a constant voltage control, a constant power control, and a constant temperature control for each of two or more terms of the control content; an output sequence specifying section (84, 85, 86, 87) adapted to specify the output sequence; a transition condition setting section (78, 79, 80, 81, 82, 83) adapted to set a temperature or a time period as a transition condition between the two or more terms; output control means adapted to control an output to the heating means based on the output sequence specified by the output sequence specifying section, an operation result by the operation means, and the temperature or the time period set by the transition condition setting section; and control selection means adapted to select one of the constant current control, the constant voltage control, the constant power control, and the constant temperature control as the control of the output control means according to the control content.