Why is going one direction faster

Okay so i have a simple basic code for moving ,]------------------

using System.Collections; using System.Collections.Generic; using UnityEngine;

public class Ballcontroller2 : MonoBehaviour {

 public float movespeed;
 private Rigidbody myrigidbody;

 private Vector3 moveInput;
 private Vector3 moveVelocity;


 // Use this for initialization
 void Start () {
     myrigidbody = GetComponent<Rigidbody> ();
     
 }
 
 // Update is called once per frame
 void Update () {
     moveInput = new Vector3 (Input.GetAxis("Horizontal"), 0f, Input.GetAxis("Vertical"));
     moveVelocity = moveInput * movespeed;
 }

 void FixedUpdate () {
     myrigidbody.velocity = moveVelocity;
 }

}

but everytime i press up and left at the same time the speed is faster than if i press up by or left by itself

is there a way to fix that so that the speed is the same? picture below should help what im saying by up-left

Thanks in advance!