A centrifugal blower includes: a centrifugal fan having plural blades arranged around a fan axis and a separation plate to blow out air in a radial direction after being sucked from one side in an axial direction; a fan casing housing the centrifugal fan; a partition plate that defines a first air passage and a second air passage arranged on the other side of the first air passage in the axial direction; and a separation cylinder arranged inside the plural blades in the radial direction. The separation cylinder expands in the radial direction as extending toward the other side in the axial direction, and is shaped to extend outward in the radial direction obliquely to the axial direction at the other end position of the separation cylinder positioned at the other end in the axial direction.