A secondary battery pack of the present invention includes a secondary battery block 3 in which a plurality of unit blocks 2 are connected in series; battery adjustment sections 5 that are each provided for each of the unit blocks 2 and have a function of monitoring the voltage of secondary batteries and a function of adjusting the balance; a charge switch 8; and a discharge switch 9. The secondary battery pack includes transmission sections 17 that receive information from the corresponding battery adjustment sections 5. The transmission sections are connected to the preceding or subsequent transmission sections and are so set that at least either information input from the preceding transmission sections or information input from the battery adjustment sections 5 is output to the subsequent transmission sections. The transmission sections are equipped with a constant current transmission section that transmits with a constant value of current; and a current detection section that can detect the value of the constant current.