The invention relates to a lithium ion battery and a fabrication method thereof, in particular to an all-solid-state lithium ion battery and a fabrication method thereof. The all-solid-state lithium ion battery comprises a positive current collector, a positive active material layer, a negative current collector, a negative active material layer and a solid electrolyte, wherein the positive active material layer is fabricated on the positive current collector by a powder method, and the negative active material layer is fabricated on the negative current collector by a thin film method. By the fabrication method, the all-solid-state lithium ion battery which has excellent integral performance, is low in production cost and is suitable for large-scale industrial production can be obtained.