Disclosed herein is a test circuit for a 3D semiconductor device for detecting soft errors and a method for testing thereof. The test circuit includes a first Multiple Input Signature Register (MISR) disposed in a first semiconductor chip, the first MISR compressing a first test result signal corresponding to a test pattern, a second MISR disposed in a second semiconductor chip stacked on or under the first semiconductor chip, the second MISR compressing a second test result signal corresponding to the test pattern, and a first error detector to detect a soft error by comparing a first output signal output from the first MISR with a second output signal output from the second MISR.