PURPOSE: To improve the connection reliability and connection life of a solder bump by making a first heat block on a mounting substrate to preheat the mounting substrate, thereafter by arranging a second heat block in the vicinity of the rear of a semiconductor chip and by heating and melting the solder bump through the radiation heat of the second heat block.

CONSTITUTION: A mounting substrate 3 is placed on a horizontal stage 6 and a first heat block 7 is made to abut on the principal plane of the mounting substrate 3 from above to preheat the mounting substrate 3. Then, a second heat block 8 is biased to the rear of a chip 2 from above to apply a suitable load to the chip 2 and to preheat the chip 2. A stopper 9a provided at the first heat block 7 is used to regulate the height of the second heat block 8. Then, after the second heat block 8 is slightly separated from the rear of the chip 2, the chip 2 is heated by the radiation heat of the heat block. When a solder bump 1 held between the electrode 4 of the mounting substrate 3 and the chip 2 is heated from both directions, the solder bump 1 melts uniformly and wet-spreads on the electrode 4 by self-alignment due to its surface tension.