A medical elongated body and a medical elongated body set are constructed in a way that expedites medical instrument insertion into a tubular body lumen via a valve body. The medical elongated body includes a tubular body insertable into a body lumen, a hub having an internal space communicating with a lumen of the tubular body and disposed in a proximal portion of the tubular body, a valve body disposed in the internal space and having an insertion portion, and a cap member that fixes the valve body in the internal space by being attached to the valve body and has a proximal opening portion to communicate with the internal space via the insertion portion. The cap member has a marker portion that guides a medical instrument inserted into the tubular body to the valve body. The marker portion has a color distinguishable from a periphery of the marker portion.