Transcanal endoscopic ear surgery (TEES) is a minimally invasive approach for treating ear diseases. TEES requires simultaneous insertion of an endoscope and surgical instruments through the narrow external auditory canal (less than 1 cm in diameter). Due to this anatomical constraint, conventional TEES has limitations including one-handed instrument manipulation and endoscope instability. We developed a compact, bed rail-mounted endoscope manipulator to enable two-handed surgery. The manipulator features three degrees of freedom: yaw and pitch movements controlled by gimbal rotational linkages, and insertion facilitated by a linear guide rail. We evaluated the mechanical performance of the prototype using an optical displacement sensor, and demonstrated positional accuracy within 0.1 mm across all axes under a 6-N load. Functionality of the manipulator was verified by cadaver trials and an ear canal model simulation. Five otolaryngologists performed a simulated surgical task using both manual and robot-assisted endoscopic procedures. While there was no significant difference in task completion time between manual and robot-assisted methods, less experienced surgeons showed improved performance and reduced time variability with the robot. The manipulator demonstrated satisfactory performance, meeting the dexterity and precision required for ear surgery. This novel endoscope-holding robot shows potential to enhance surgical precision and efficiency in TEES, particularly benefiting less experienced surgeons. Future iterations will aim to optimize its form factor and functional complexity to enhance clinical utility.