To provide a transmission capable of: reducing horsepower loss by reducing the amount of lubricating oil for a power transmission system including speed gears when the present speed gear is a specified gear of the speed gears; and securing the lubricating oil amount for the transmission system during a shift performed when the present gear is the specified speed gear. The transmission includes: the power transmission system; a lubricating oil amount reducing mechanism for reducing the lubricating oil amount supplied to the power transmission system when the present gear is the specified speed gear; and controller for determining a shift point vehicle speed pertaining to the specified speed gear based on a preset shift map, and activating the oil amount reducing mechanism, when a difference between the shift point vehicle speed and actual vehicle speed exceeds a first predetermined value and while the specified speed gear is the present gear.