A boost control apparatus (30) is provided with: a controlling device (330) configured (i) to perform first duty control by using a first control parameter if output current (IL) that flows through an inductor (L1) is not near zero, and (ii) to perform second duty control by using a second control parameter if the output current is near zero, during one-side element control during which only either one of a first switching element (Q1) and a second switching element (Q2) is driven; a rate calculating device (310) configured to calculate a change rate of the output current to a change amount of a duty value in the first duty control and the second duty control; and a control determining device (320) configured to control said controlling device to perform the second duty control regardless of the output current, if the change rate is less than a predetermined value.