In graded‐index and step‐index fibers, splicing loss was measured under the condition that all the guided modes are equally excited by light‐emitting diodes. Measurements were made both for short and long fibers. For a short fiber, the graded‐index fiber has a larger splicing tolerance to misalignment than the step‐index fiber; while for a long fiber the former was somewhat more sensitive than the latter. This difference can be interpreted as showing that leaky modes, excited by transverse displacement in graded‐index fibers, affect transmission loss.