After introducing minimally invasive surgery, robotic surgery has been increasingly used in colorectal cancer. However, there is a few prospective study for robotic surgery. The aim of this trial is to evaluate the effectiveness and safety of robotic surgery in mid or low rectal cancer.

This study was designed as randomized phase II trial (laparoscopic versus robotic). The primary end point is quality of mesorectal excision.

Inclusion Criteria:

• mid or low rectal cancer (within 9cm from anal verge)
• pathologically proven as adenocarcinoma
• written informed consent
• no severe functional disability in lung and heart

Exclusion Criteria:

• invading adjacent organ
• distant metastasis (lung, liver, brain, bone, distant lymph nodes etc.)
• lateral pelvic lymph node metastasis
• Have severe concomitant disease that might limit compliance or completion of the protocol.
• Have any other malignancy that might impact 5-year survival or might be potentially confused with rectal cancer.
• If female, be pregnant or breast feeding.
• Hereditary colorectal cancer (HNPCC, FAP etc)
• emergency operation