  A largely extended X-ray emission was discovered around the pulsar PSR
J1357-6429 with the Suzaku deep observations. The pulsar, whose characteristic
age is 7.3 kyr, is located within the TeV gamma-ray source HESS J1356-645. The
extended emission is found to have a 1sigma X-ray size of ~4 arcmin, or ~3 pc
at 2.4 kpc, with a small offset from the pulsar. Its X-ray spectrum is well
reproduced by a simple power-law model with a photon index of 1.70+0.07-0.06.
No significant spatial variation was found for the X-ray photon index as a
function of distance from the pulsar. We conclude that the extended emission is
associated to the pulsar wind nebula of PSR J1357-6429. This is a new sample of
largely extended nebulae around middle-aged pulsars. We discuss the evolution
of this PWN according to the relic PWN scenario.
