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.