Provided are an aluminum paste composition capable of inhibiting formation of blisters and globules of aluminum in a back surface electrode layer, which is caused at the time of firing, of reducing bow of a silicon semiconductor substrate even when a thinner silicon semiconductor substrate is used, and of attaining a high BSF effect and a high energy conversion efficiency; and a solar cell element comprising an electrode formed by using the composition. The aluminum paste composition is a paste composition for forming an electrode (8) on a silicon semiconductor substrate (1), comprising: aluminum powder; an organic vehicle; and a plasticizer. The solar cell element comprises the electrode (8) formed by applying on the silicon semiconductor substrate (1) the paste composition having the above-mentioned features and thereafter, firing the paste composition.