Abstract: A gate valve, a substrate processing apparatus, and a substrate processing method which can improve the airtightness and cleanliness of a vacuum processing chamber and a vacuum preliminary chamber. A gate valve has a face facing a vacuum processing chamber and a face facing a vacuum preliminary chamber, the faces abutting on annular sealing members surrounding entire circumferences of substrate loading/unloading ports of the vacuum processing chamber and the vacuum preliminary chamber, and openably and closably connects the vacuum processing chamber and the vacuum preliminary chamber. The gate valve includes sealing channels provided between the sealing members doubly provided outside and inside surrounding the entire circumference of at least one of the substrate loading/unloading ports and between other sealing members doubly provided outside and inside in one or more parts inside the gate valve, and a gas circulation channel including the sealing channels.