A driving assistance device (10), wherein a required starting space estimating unit (12) estimates a required starting space, which is the space required by a host vehicle for completion of starting. A required starting time estimating unit (14) calculates an estimated required starting time, which is an estimated value of the time required for completion of starting during starting of the host vehicle. A collision time estimating unit (13) calculates an estimated collision time, which is an estimated value of the time until an obstacle reaches the required starting space. A starting margin calculating unit (15) calculates a starting margin on the basis of the estimated required starting time and the estimated collision time, the starting margin indicating a temporal margin for completing the starting of the host vehicle by the time the obstacle reaches the required starting space. A notification processing unit (16) notifies the driver of the host vehicle of the starting margin.