A method and equipment for adjusting the temperature of glass sheets in a tempering furnace. The tempering furnace (1) comprises rollers (3) for conveying and oscillating the glass sheets (4) during heating, and resistors (5, 6) for heating the glass sheets (4) from above and from below. The temperature of the glass sheets (4) is measured inside the tempering furnace (1) during heating and the dwell time of the glass sheets (4) in the furnace is adjusted based on the temperature measurements. This enables exact control of the final temperature of the glass from the beginning, and the temperature can be kept uniform independently of the measures taken by the operator.