The invention provides a control device for a vehicle power transmission device, which can improve the determination precision of the working state of a second engaging device. Based on a state of hydraulic control for the second clutch (C2) and a state of a rotational speed difference (Nc2) of the second clutch (C2), it is determined whether or not a transition condition of an operating state ofa second clutch (C2) represented by four states of complete release, complete engagement, release transition, and engagement transition has been established; determining whether the transfer conditionis established or not based on the result. Determining an operating state of the second clutch (C2); accordingly, it is possible to appropriately determine four states of the second clutch (C2) by taking into account the actual state of the second clutch (C2) in the tendency that the clutch hydraulic pressure of the second clutch (C2) is rising or falling and/or the state of the instruction hydraulic pressure of the second clutch (C2). Therefore, it is possible to improve the determination accuracy of the operating state of the second clutch (C2).