Disclosed is a library device in which the space to enlarge the magazine can be secured to the rear side of the library device. The library device includes power supply means for supplying electricity to the library device, medium housing means which can house a plurality of computer-readable media, medium reading/writing means for reading/writing data from/to the medium, medium conveying means for conveying the medium between the medium housing means and the medium reading/writing means, control means for controlling operation of the library device and first connection means to which the power supply means and the control means can be electrically connected when these means are installed and from which the power supply means and the control means can be disconnected when these means are extracted. The power supply means, the first connection means, and the control means are disposed along any one of two sides of the library device, and one of the first connection means is disposed between the power supply means and the control means and whereby, the first connection means is connected to the power supply means and the control means.