A method is provided for firmly connecting a connector terminal to a flat conductor. This is a method for electrically connecting the pierce terminal 20 having pierce blades 21 that pierce through the flat conductor 102 with the flat conductor 102 by the pierce blades 21, in which the connection state is adjusted based on a terminal reaction force R acting on the pierced blade 21a by a ruptured end surface 102a of the flat wiring conductor 102. The adjustment of the terminal reaction force R is made by adjusting a pressing reaction force F/A generated when the pierce blade 21 pierces through the flat wiring conductor 102.