The invention relates to a medium processing apparatus and a medium transaction device. A cash automatic transaction device is provided with a bill inlet and outlet portion for delivery of a paper sheet-like medium with an operator; a conveying portion conveying a bill that the bill inlet and outlet portion receives or should discharge; a cash pool backet in a substantially box shape formed by metal plates that are difficult for electric waves to pass through; a bill control portion configured outside the cash pool basket; an upper wireless substrate communicating with the bill control portion; a bill storage pool and a bill rejection pool which are configured inside the cash pool basket and capable of bill storage; and a lower wireless substrate being disposed at the bill storage pool and the bill rejection pool, being in wireless communication with the upper wireless substrate and controling the bill storage pool and the bill rejection pool, and an electric wave opening portion disposed at the cash pool basket to enable electric waves for wireless communication between the upper wireless substrate and the lower wireless substrate to pass between the outside and the inside of the cash pool basket.