A tire for a motorcycle comprising a tread portion, wherein the tread portion is provided with main grooves each having a groove width larger than 2 mm and narrow grooves each having a groove width not more than 2 mm, the main grooves include first main grooves and second main grooves arranged on an outer side in a tire axial direction of the first main grooves, the narrow grooves include open narrow grooves and semi-open narrow grooves, each of the open narrow grooves is arranged such that one end thereof is substantially connected with adjacent one of the first main grooves and the other end thereof is substantially connected with adjacent one of the second main grooves, and each of the semi-open narrow grooves has a first end and a second end, and the first end is substantially connected with adjacent one of the first main grooves or the second main grooves and the second end terminates on a ground contacting surface of the tread portion without being substantially connected with any one of the main grooves, wherein the expression "substantially connected" means that in a longitudinal direction of one of the narrow grooves, the end (7a, 7b, 8a, 8b) is connected with its adjacent one of the main grooves or a shortest distance between the end (7a, 7b, 8a, 8b) and its adjacent one of the main grooves is less than 5% of a tread development half width (Ta), c h a r a c t e r i z e d in that the semi-open narrow grooves include first semi-open narrow grooves whose first ends are substantially connected with the first main grooves and second semi-open narrow grooves whose first ends are substantially connected with the second main grooves. the tread portion is provided with main grooves each having a groove width larger than 2 mm and narrow grooves each having a groove width not more than 2 mm, the main grooves include first main grooves and second main grooves arranged on an outer side in a tire axial direction of the first main grooves, the narrow grooves include open narrow grooves and semi-open narrow grooves, each of the open narrow grooves is arranged such that one end thereof is substantially connected with adjacent one of the first main grooves and the other end thereof is substantially connected with adjacent one of the second main grooves, and each of the semi-open narrow grooves has a first end and a second end, and the first end is substantially connected with adjacent one of the first main grooves or the second main grooves and the second end terminates on a ground contacting surface of the tread portion without being substantially connected with any one of the main grooves, wherein the expression "substantially connected" means that in a longitudinal direction of one of the narrow grooves, the end (7a, 7b, 8a, 8b) is connected with its adjacent one of the main grooves or a shortest distance between the end (7a, 7b, 8a, 8b) and its adjacent one of the main grooves is less than 5% of a tread development half width (Ta), c h a r a c t e r i z e d in that the semi-open narrow grooves include first semi-open narrow grooves whose first ends are substantially connected with the first main grooves and second semi-open narrow grooves whose first ends are substantially connected with the second main grooves.