A packet inspection device and method for use with a packet-retrievable network apparatus are provided. The packet inspection method includes: converting header information of a packet received into a hashing function value in presence of handshaking underway at the Transmission Control Protocol (TCP) layer and comparing the hashing function value by a hashing function unit of the pending processing module, storing the hashing function value in a memory unit, and performing packet state comparison and packet screening and then creating by the session processing module a transmission connection according to the packet screened and selected by the pending processing module upon determination that data stored in the memory unit match the hashing function value resulting from conversion by the hashing function unit, thereby expediting packet inspection, reducing occupied memory space, and cutting costs.