A mobile power device includes a mobile power source and a border casing. The mobile power source includes a housing, and the housing has a top plate and an annular plate. The border casing encloses the annular plate. An inner circumference of the border casing has a surrounding block surroundingly disposed around the top plate. The surrounding block protrudes beyond the top plate, and a gap is formed between the surrounding block and the top plate. Therefore, the surrounding block can restrict a position of a portable electronic product, so that the portable electronic product is securely disposed corresponding to the mobile power source to enhance the convenience in using the mobile power device.