In this paper, a measurement method for cross-sectional temperature distributions is considered. A novel method based on an acoustic computed tomography (CT) technique is proposed. Specifically, the temperature distributions are estimated using the time of flight data of many ultrasonic propagation paths. The Maximum Likelihood - Expectation Maximization (ML-EM) method is proposed to reconstruct the temperature distributions in a square area properly. The effectiveness of the proposed reconstruction method is confirmed by both numerical experiments and fabricated experimental system.