Electric seat mechanical extension device and electric seat

An electric seat mechanical extension device, comprising two mechanical extending units bilaterally symmetrical with each other, wherein each of the two mechanical extending units is composed of a seat frame support assembly, a leg assembly and a backrest bar, the two mechanical extending units are connected through a drive fixing assembly and a driving rod, a driving device is mounted on the drive fixing assembly, a head of the driving device is articulated with the driving rod, and the driving rod is connected with the leg assemblies,

• wherein the seat frame support assembly is composed of a fixing rod and a transmission rod, the fixing rods are fixedly connected with the drive fixing assembly, front portions of the fixing rods are articulated with second leg links through second leg link and fixing rod articulation shafts, rear portions of the fixing rods are articulated with the backrest bars through fixing rod and backrest bar articulation shafts, backrest lying position retainers are arranged on the backrest bars, and lower portions of the backrest bars are articulated with rear ends of the transmission rods through transmission rod and backrest bar articulation shafts.