A computer host having two layers inside includes a chassis, a partition, a first circuit board, a second circuit board, and an electrical connecting device. The partition divides the interior of the chassis into a first accommodation space and a second accommodation space. The first circuit board and the second circuit board are disposed on two sides of the partition respectively, and are respectively located in the first accommodation space and the second accommodation space. The electrical connecting device is used to electrically connect the first circuit board and the second circuit board, so that the first and second circuit boards together form a complete electronic circuit system for the operation of the computer host.