A traveling support device includes: a road-vehicle communication portion that receives first current-signal information relating to a signal displayed by a traffic signal at a first clock time, from a road side transmitter installed on a road; an inter-vehicle communication portion that receives second current-signal information relating to a signal displayed by the traffic signal at a second clock time, from another vehicle that receives the second current-signal information from the road side transmitter; and a signal cycle estimating portion that estimates signal cycle information relating to transition of the signal on the traffic signal on the basis of the first current-signal information received by the road-vehicle communication portion and the second current-signal information received by the inter-vehicle communication portion.