diff --git a/sub_project/models/sub_project.py b/sub_project/models/sub_project.py
index 6bc1a1d..3168042 100755
--- a/sub_project/models/sub_project.py
+++ b/sub_project/models/sub_project.py
@@ -6,4 +6,6 @@ class SubProject(models.Model):
     _description = "Sub Project"
 
     is_sub_project = fields.Boolean("Is Sub Project")
-    sub_project = fields.Many2one('project.project', string='Sub Project')
\ No newline at end of file
+    sub_project = fields.Many2many('project.project', 'project_subproject_rel', 'project_id',
+                              'id', string='Sub Project')
+
diff --git a/sub_project/views/sub_project.xml b/sub_project/views/sub_project.xml
index 5a79b6a..1ced844 100755
--- a/sub_project/views/sub_project.xml
+++ b/sub_project/views/sub_project.xml
@@ -14,7 +14,7 @@
                                 <field name="is_sub_project"/>
                             </group>
                             <group>
-                                <field name="sub_project" attrs="{'invisible': [('is_sub_project', '=', False)], 'required': [('is_sub_project', '=', True)]}"
+                                <field name="sub_project" widget="many2many_tags" attrs="{'invisible': [('is_sub_project', '=', False)], 'required': [('is_sub_project', '=', True)]}"
                                        options="{'no_open': True, 'no_create': True, 'no_create_edit': True}"/>
                             </group>
                         </page>