  In this article, we reformulate the cobordism map of embedded contact
homology, which is induced by exact symplectic cobordism and defined as direct
limit of homomorphisms called filtered ECH cobordism map. The filtered ECH
cobordism map is defined by counting embedded holomorphic curves with zero ECH
index and we prove that it is independent on almost complex structure by
Seiberg Witten theory. Moreover, our definition in fact is equivalent to the
existing definition.
