Heat exchanger and method for manufacturing the same

A method for manufacturing a heat exchanger including a box-shaped tank, a box-shaped base plate and a tube, said method comprising:

• cutting a metal plate to make an unfolded metal plate for forming said box-shaped tank;
• cutting a metal plate to make an unfolded metal plate for forming said base plate and making a hole into which said tube is inserted at said base plate, said unfolded metal plate for forming said box-shaped tank and said base plate being formed by:
• forming a body portion in a rectangular shape having a pair of long sides and a pair of short sides;
• forming a pair of first folded portions along said long sides of said body portion;
• and
• forming a pair of second folded portions along said short sides of said body portion;
• folding and joining said first and second folded portions of said metal plate for said tank along a predetermined folding line to form said tank in a box shape having an opening;
• folding and joining said first and second folded portions of said metal plate for said base plate along a predetermined folding line to form said base plate in a box shape having an opening;
• inserting an end portion of said tube into said hole of said base plate and assembling said tank with said base plate to cover said opening of said tank;
• and
• brazing said tank and said base plate and said tube integrally to make an assembled body.