Security design planning support device

A security design support device which supports a security design of an in-vehicle network, comprising:

• a strategy policy creation circuit which creates first strategy policy information representing a plurality of control strategies corresponding respectively to threats against the in-vehicle network;
• a merge processing circuit which merges control strategies of a same type among the plurality of control strategies represented by the first strategy policy information created by the strategy policy creation circuit and groups the merged plurality of control strategies;
• and
• a communication device which outputs second strategy policy information representing a relationship of the threats and the plurality of merged control strategies grouped by the merge processing circuit, wherein
• the communication outputs the second strategy policy information to an external computer, and wherein
• the second strategy policy information is information for displaying, on a display device of the computer, a screen indicating a relationship of the threats and the plurality of merged control strategies grouped by the merge processing circuit.