To make the Button have rounded corners right click on res->drawable folder and select Other

Now Select Android -> Android XML File

Now add a File Name and Select shape from Root Element

Add android:shape="rectangle" attribute in <shape> tag. Now add a <corner> tag within the <shape> tag and add attribute android:radius tag with value in dp. You can also set individual corner radius by,
<corners
android:bottomLeftRadius="10dp"
android:bottomRightRadius="10dp"
android:topLeftRadius="10dp"
android:topRightRadius="10dp" />
android:bottomLeftRadius="10dp"
android:bottomRightRadius="10dp"
android:topLeftRadius="10dp"
android:topRightRadius="10dp" />
Example : button.rounded.xml
<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle" >
<stroke
android:drawable="@android:color/transparent"
android:width="1dp"
android:color="#CC888888" >
</stroke>
<solid android:color="#FFFFFF" />
<corners
android:bottomLeftRadius="10dp"
android:bottomRightRadius="10dp"
android:topLeftRadius="10dp"
android:topRightRadius="10dp" />
</shape>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle" >
<stroke
android:drawable="@android:color/transparent"
android:width="1dp"
android:color="#CC888888" >
</stroke>
<solid android:color="#FFFFFF" />
<corners
android:bottomLeftRadius="10dp"
android:bottomRightRadius="10dp"
android:topLeftRadius="10dp"
android:topRightRadius="10dp" />
</shape>
In your Layout.xml where you have created your Button, you need to add an attribute android:background="@drawable/button_rounded".
<Button
android:id="@+id/button1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true"
android:background="@drawable/button_rounded"
android:layout_marginTop="154dp"
android:text="Button" />
android:id="@+id/button1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentTop="true"
android:layout_centerHorizontal="true"
android:background="@drawable/button_rounded"
android:layout_marginTop="154dp"
android:text="Button" />
Output
