To easily generate the arrangement drawing of complicated cable trays and, moreover, to facilitate arrangement design by removing an unnecessary line in accordance with an intersecting state and also displaying the lower side tray by means of a broken line in a part where the cable trays cross each other based on composite data.

A hidden line processing part 2 executes a processing for displaying the lower side tray of the part where the cable trays are longitudinally mutually superposed based on composite data by the broken line. An envelope processing part 3 removes the unnecessary line in accordance with the intersecting state and also displays the lower side tray by the broken line in the part where the cable trays mutually cross based on composite data. Then, tray data is inputted as composite data consisting of arrangement data and its attributedata so as to automatically discriminate the positional relation of the trays and to execute a hidden line processing concerning vertical position relation and an enveloping processing concerning the intersecting part. Therefore, the arrangement chart of the cable trays are easily generated.