A transmission control device may be provided that includes a magnet, a magnetic sensor, a slider, a shift lever, and a motion conversion member. The magnetic sensor is fixed to a predetermined position and measures a magnetic field which changes according to a relative position with respect to the magnet. The magnet is disposed at one end of the slider. The shift lever rotates to a position according to a shift level by user operations. When the shift lever rotates, the motion conversion member converts a rotational motion of the shift lever into a linear motion, and moves the slider in a first direction.