A vacuum forming apparatus includes a die set including an upper die and a lower die. The upper die is configured to move in a horizontal direction from a normal position at which the upper die is initially set. The lower die includes a suction channel through which a vacuum is applied to a cover. The lower die is opposite the upper die that is at the normal position. The upper die is configured to move from the normal position to a space lateral to the lower die so as not to face the lower die after the die set is opened, and return to the normal position before the die set is closed. The lower die is configured to move downward during opening of the die set and upward during closing thereof. The die set is configured to form the base member with the cover into a predetermined shape.