Existing monocular visual simultaneous localization and mapping (SLAM) mainly focuses on point and line features, and the constraints among line features are not fully explored. In this paper, a multi-feature monocular SLAM with ORB points, lines, and junctions of coplanar lines is proposed for indoor environments. To create 3D junctions of coplanar lines, an adaptive coordinate confidence is designed to describe the coordinate stability of 2D junctions on the image plane. Based on the matched 2D junctions between the current keyframe and other two associated keyframes, a multi-view coplanarity verification is performed for 3D junction creation. Moreover, reprojection verification is conducted to update the observation of 3D junction, which is used to dynamically update the confidence of coplanarity for confidence-based local bundle adjustment. The camera pose is optimized through multiple constraints of ORB points, lines, and junctions of the coplanar lines. As a result, the performance of monocular SLAM is improved. The experiment verification shows the effectiveness of the proposed method.