A medical overtube to be inserted into a body cavity, the medical overtube including a flexible elongated part having a channel through which an elongated medical device is inserted, and a tubular distal end portion connected to a distal end of the elongated part. The distal end portion includes a first section having an end opening which forms an opening of the channel, and a second section located next to a base-end side of the first section, and the medical overtube satisfies the Conditional Expressions K1>K2 and K3>K2, where K1 is rigidity of the first section, K2 is rigidity of the second section, and K3 is rigidity of the elongated part.