Memory modlue mounting method and memory module device using thereof

A method of mounting memory modules and a memory module device are provided to fold a flexible PCB(Printed Circuit Board) to which a plurality of memory modules are attached and mount the memory modules on a substrate while the memory modules are vertically arranged. A plurality of memory modules(110) is attached to a flexible PCB(120) on which a first connector(122) is formed. The flexible PCB is folded for at least one memory module. A module chassis(130) having an internal space(132) for surrounding and supporting the flexible PCB is mounted on a substrate(140) on which a second connector(142) is formed. The flexible PCB is inserted into the internal space of the module chassis and the first connector is connected to the second connector so as to mount the memory modules on the substrate.