Shift control method and shift control system

A shift control system for a vehicle having an automatic transmission and a shift control device controlling an input shaft rotation speed of the automatic transmission to a target input shaft rotation speed during a shift, wherein

• the shift control device comprises:
• a basic target synchronization rotation speed set unit configured to set a basic target synchronization rotation speed that is a basic target value of the input shaft rotation speed during the shift:
• and
• a rotation speed decreasing correction unit configured to:
• when the shift is a downshift, determine whether or not the downshift is a coast downshift, the coast downshift being the downshift without a requirement for a driving force of the vehicle;
• and
• if it is determined that the shift is not the coast downshift,
• set the basic target synchronization rotation speed as the target input shaft rotation speed,
• if it is determined that the shift is the coast downshift,
• set a corrected target input shaft rotation speed as the target input shaft rotation speed, the corrected target input shaft rotation speed being obtained by decreasingly correcting the basic target synchronization rotation speed, wherein
• the rotation speed decreasing correction unit is configured to set a decreasing correction amount of the basic target synchronization rotation speed so as to become larger as a deceleration of the vehicle becomes larger.