A secondary battery pack comprising: an anode terminal and a cathode terminal of a battery cell connected to a protection circuit module (PCM, 120), the anode terminal and the cathode terminal of the battery cell being made of plate-shaped conductive members; the battery cell having the anode terminal and the cathode terminal formed at one end thereof, the battery cell having a thermally bonded surplus part formed at the end thereof at which the anode terminal and the cathode terminal are formed; and the PCM comprising a protection circuit board (PCB, 122) having a protection circuit formed thereon, an external input and output terminal connected to the protection circuit of the PCB, and an electrically insulative PCM case configured to have a hollow structure in which the PCB is mounted, the PCM case being provided with a slit, through which the electrode terminals (112, 114) of the battery cell are inserted, the PCM being loaded on the thermally bonded surplus part of the battery cell in a state in which the PCM is electrically connected to the battery cell, characterized in that - the anode terminal and the cathode terminal of the battery cell and the external input and output terminal of the PCM are inserted through a slit from one end of the PCM case such that the PCB is mounted into the PCM case, - the PCB is mounted into the PCM case in a sliding fashion, - the PCM case is formed in the shape of a quadrangular bar having a hollow structure and the quadrangular bar is open at opposite ends thereof and the slit is formed at an edge of one side of the quadrangular bar, and - the external input and output terminal is connected to the PCB disposed in the PCM case through the slit. an anode terminal and a cathode terminal of a battery cell connected to a protection circuit module (PCM, 120), the anode terminal and the cathode terminal of the battery cell being made of plate-shaped conductive members; the battery cell having the anode terminal and the cathode terminal formed at one end thereof, the battery cell having a thermally bonded surplus part formed at the end thereof at which the anode terminal and the cathode terminal are formed; and the PCM comprising a protection circuit board (PCB, 122) having a protection circuit formed thereon, an external input and output terminal connected to the protection circuit of the PCB, and an electrically insulative PCM case configured to have a hollow structure in which the PCB is mounted, the PCM case being provided with a slit, through which the electrode terminals (112, 114) of the battery cell are inserted, the PCM being loaded on the thermally bonded surplus part of the battery cell in a state in which the PCM is electrically connected to the battery cell, characterized in that - the anode terminal and the cathode terminal of the battery cell and the external input and output terminal of the PCM are inserted through a slit from one end of the PCM case such that the PCB is mounted into the PCM case, - the PCB is mounted into the PCM case in a sliding fashion, - the PCM case is formed in the shape of a quadrangular bar having a hollow structure and the quadrangular bar is open at opposite ends thereof and the slit is formed at an edge of one side of the quadrangular bar, and - the external input and output terminal is connected to the PCB disposed in the PCM case through the slit. - the anode terminal and the cathode terminal of the battery cell and the external input and output terminal of the PCM are inserted through a slit from one end of the PCM case such that the PCB is mounted into the PCM case, - the PCB is mounted into the PCM case in a sliding fashion, - the PCM case is formed in the shape of a quadrangular bar having a hollow structure and the quadrangular bar is open at opposite ends thereof and the slit is formed at an edge of one side of the quadrangular bar, and - the external input and output terminal is connected to the PCB disposed in the PCM case through the slit.