Although many papers about the interleaved boost converter(IBC) have been published, there are, unfortunately, no analytical and rigorous expressions for steady-state operation of the N-phase IBC. To understand the operating characteristics of the N-phase IBC, the averaged state equation and the general steady-state solutions are derived in this paper. The general expressions of the current unbalance due to the parameter mismatch, the inductor and input current ripples, and the output voltage ripple are also presented. Through the analytical expressions presented, the steady-state characteristics of the N-phase IBC are analyzed theoretically and verified experimentally.