A drive power transmission device is provided that either disengages a first friction engagement element or a second friction engagement element when the other is engaged. The drive power transmission device detects the temperature of lubricating oil flowing in each friction engagement element using a temperature sensor. The drive power transmission device selectively disengages either a forward clutch or a reverse brake disengages when the other is engaged. The forward clutch and the reverse brake overlap axially, and are layered radially in an inner/outer arrangement. The temperature sensor is positioned at the periphery of the forward clutch and the reverse brake. A lubricating oil pathway is formed such that lubricating oil for cooling the forward clutch and the reverse brake passes through the forward clutch and the reverse brake in the radial direction from the inside of the forward clutch and the reverse brake to the temperature sensor.