Unity GUI Font Size changes with the screen resolution Problem

I am working on a project and now I have a problem . The problem is the font size. The font size is OK inside the Unity but it is really small when I play the game on a real Android device .

My Canvas has 2 text and 1 image .

I created a empty game object to hold that text.

Here is the code attached to empty game object :-

 using UnityEngine;
 using System.Collections;
 using UnityEngine.UI;
 
 
 public class Text_Script : MonoBehaviour 
 {
 
 public Text My_Text_1 ;
 public Text My_Text_2 ;
 
 // Use this for initialization
 void Start () 
 {
     My_Text_1.text = "Hello";
     My_Text_2.text = "World";
 }
 
 // Update is called once per frame
 void Update () 
 {
 
 }
 }

Here are the images :-

Inside Unity

Inside a Android Device (here I uploaded the image from BlueStacks , I didn't use my mobile)

So why this is happening ?

I tried this :-

 function Start() 
 {
      var myText = GetComponent(GUIText);
      // 50 is the fontsize you want to use
      myText.fontSize = Mathf.Min(screen.height,screen.width)/50;
 }

but I don't know where to put and on which object should I put those code And I am using Unity 5 and that code is for Unity 4.x .

I don't want to scale the font for a large size as explained in YouTube video (https://www.youtube.com/watch?v=_9mOh7_xX2o) (I don't think this is a good method)

So is there any ways to change the font size according to the screen size and resolution .

Please help me

Thanks:)