To optimize procedures relevant to trading orders of securities carried out by a trading procedure agent of a securities company or a securities intermediary on the basis of a request of a customer.

In the method of trading securities, information necessary for assisting judgement accompanying trading of securities by the customer or judging propriety of trading contents is provided to an outside checker by receiving a trading order from a trading procedure agent terminal device 20 by a securities company server 40, sending trading order information to a server 70 for outside checking, and sending information for outside checking including the trading order information from the server 70 to an outside checker terminal device 30. An ordering process is carried out by the securities company server 40 in accordance with ordering permission information from the outside checker terminal device 30 based upon the judgement of the outside checker.