An electrical power conversion apparatus includes a high-voltage bus bar, a low-voltage bus bar, and a relay bus bar which are integrated together in the form of a bus bar assembly. The high-voltage bus bar includes semiconductor-side high-voltage terminals and capacitor-side high-voltage terminals. The low-voltage bus bar includes semiconductor-side low-voltage terminals and capacitor-side low-voltage terminals. The relay bus bar includes a reactor-side relay terminal and a capacitor-side relay terminal 532. The capacitor-side high-voltage terminals, the capacitor-side low-voltage terminals, and the capacitor-side relay terminal are arranged in the form of a terminal array. The capacitor-side high-voltage terminals and the capacitor-side low-voltage terminals are arranged adjacent each other. The capacitor-side relay terminal is located at an end of an array of the capacitor-side high-voltage terminals and the capacitor-side low-voltage terminals. With these arrangements, the electrical power conversion apparatus is capable of reducing the inductance and facilitating the assembling and downsizing thereof.