A printed wiring board comprises a main board and a pair of rows of connection terminals for holding a card board in a vertical position. Each connection terminal is inserted into the main board at a predetermined interval, and electrically connected with a circuit pattern of the main board. The printed wiring board allows the card board to be positioned vertically on the main board, and is adaptable to change the number of patterned external connection terminals of the card board. A guide means with resilient tongues may be provided at the respective ends of the rows to additionally secure the card board in place.