Measuring Range of Motion (ROM) is the first step of physical therapy. A new method to measure ROM by Kinect V2 whose camera type is time of flight is proposed. Colored markers are attached to related joints and then their camera centered three-dimensional world coordinates are located by Kinect Using these coordinates, joint angle, and ROM can be accurately calculated. To analyze reliability and validity of the method, ROM measurements of right and left elbow from ten participants are taken by standard goniometer and Kinect separately. For inter-observer reliability, measurements were taken in two sessions by three physiotherapists. The reliability tests Intra-class Correlation Coefficient (ICC), Standard Error of Measure (SEM), and Minimal Detectable Change (MDC) belonging to the measurements have been obtained. To compute absolute accuracy of the method, a goniometer marked with colors has been recorded at four different angles (45, 90, 135, and 180 degrees) by Kinect in six sessions having 50-frame periods each. Mean, Standard Deviation (SD), Root Mean Square Error (RMSE), and Limits of Agreement (LOA) values are given for each angle and session. The measurements taken for absolute accuracy clearly shows that Kinect has 1- to 3-degree error rate and below 1-degree standard deviation. Analyzing the collected data, the ICC values of Kinect measurements that are 0.94 for right arm and 0.93 for left arm in contrast with the ICC values of goniometric measurements taken by observers are 0.78 for the right arm and 0.81 for the left arm. This study indicates the proposed method has a high level of accuracy and reliability, and it can be efficiently used to measure ROM accurately.