Provided is a ventilation device that can prevent infiltration of rainwater and ensure an increased rate of ventilation. A ventilation device (1) that is provided with a plurality of louver units (2). The plurality of louver units (2) have: an outer vane (3) that is inclined such that a lower edge thereof is positioned on an indoor side; and an inner vane (4) that is inclined such that a lower edge thereof is positioned on an outdoor side. One shielding part (42) of one louver unit (2A) touches a straight line (L1) that connects an upper-end part of one shielding part (32) of another louver unit (2B) and an upper-end part of another shielding part (42) of the other louver unit (2B), and another shielding part (32) of the one louver unit (2A) touches a straight line (L2) that connects the upper end of the one shielding part (32) of the other louver unit (2B) and an upper end part of the one shielding part (42) of the one louver unit (2A).
