To improve the operability when a by-pass capacitor is arranged by recognizing a bundle of lines from component connection information and generating a block using components connected by the bundle of lines as one memory component.

On the basis of component connection information and component shape information read in a storage means 12, a memory recognizing means 16 detects components judges as memory components among components arranged on a printed board, forms a block by collecting the detected components, and stores it as block information in the component shape information. Further, a by-pass capacitor allocating and integrating means 18 properly allocates a by-pass capacitor to the block of the components generated by the memory recognizing means 16 according to the component shape information including the block information and design rule information, integrates them as a virtual component, and stores information showing the virtual component additionally to the component shape information. According to the information whose storage contents are thus updated, etc., a component arranging means 20 arranges the components on the printed board.